Config(3)

NAME
Config - access Perl configuration information

SYNOPSIS

    use Config;
    if ($Config{'cc'} =~ /gcc/) {
        print "built by gcc\n";
    }
    use Config qw(myconfig config_sh config_vars);
    print myconfig();
    print config_sh();
    config_vars(qw(osname archname));

DESCRIPTION
The Config module contains all the information that was available to the Configure program at Perl build time (over 900 values).

Shell variables from the config.sh file (written by Configure) are stored in the readonly-variable %Config, indexed by their names.

Values stored in config.sh as 'undef' are returned as undefined values. The perl exists function can be used to check if a named variable exists.

myconfig()
    Returns a textual summary of the major perl configuration values. See also -V in the Switches entry in the perlrun manpage.

config_sh()
    Returns the entire perl configuration information in the form of the original config.sh shell variable assignment script.

config_vars(@names)
    Prints to STDOUT the values of the named configuration variable. Each is printed on a separate line in the form:

      name='value';
    Names which are unknown are output as name='UNKNOWN';. See also -V:name in the Switches entry in the perlrun manpage.

EXAMPLE
Here's a more sophisticated example of using %Config:

    use Config;
    use strict;
    my %sig_num;
    my @sig_name;
    unless($Config{sig_name} && $Config{sig_num}) {
        die "No sigs?";
    } else {
        my @names = split ' ', $Config{sig_name};
        @sig_num{@names} = split ' ', $Config{sig_num};
        foreach (@names) {
            $sig_name[$sig_num{$_}] ||= $_;
        }
    }
    print "signal #17 = $sig_name[17]\n";
    if ($sig_num{ALRM}) {
        print "SIGALRM is $sig_num{ALRM}\n";
    }

WARNING
Because this information is not stored within the perl executable itself it is possible (but unlikely) that the information does not relate to the actual perl binary which is being used to access it.

The Config module is installed into the architecture and version specific library directory ($Config{installarchlib}) and it checks the perl version number when loaded.

The values stored in config.sh may be either single-quoted or double-quoted. Double-quoted strings are handy for those cases where you need to include escape sequences in the strings. To avoid runtime variable interpolation, any $ and @ characters are replaced by \$ and \@, respectively. This isn't foolproof, of course, so don't embed \$ or \@ in double-quoted strings unless you're willing to deal with the consequences. (The slashes will end up escaped and the $ or @ will trigger variable interpolation)

GLOSSARY
Most Config variables are determined by the Configure script on platforms supported by it (which is most UNIX platforms). Some platforms have custom-made Config variables, and may thus not have some of the variables described below, or may have extraneous variables specific to that particular port. See the port specific documentation in such cases.

  M

Mcc From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the Mcc program. After Configure runs, the value is reset to a plain Mcc and is not useful.

  _

_a  From Unix.U:

    This variable defines the extension used for ordinary libraries. For unix, it is .a. The . is included. Other possible values include .lib.

_exe
    From Unix.U:

    This variable defines the extension used for executable files. For unix it is empty. Other possible values include .exe.

_o  From Unix.U:

    This variable defines the extension used for object files. For unix, it is .o. The . is included. Other possible values include .obj.

  a

afs From afs.U:

    This variable is set to true if AFS (Andrew File System) is used on the system, false otherwise. It is possible to override this with a hint value or command line option, but you'd better know what you are doing.

alignbytes
    From alignbytes.U:

    This variable holds the number of bytes required to align a double. Usual values are 2, 4 and 8.

ansi2knr
    From ansi2knr.U:

    This variable is set if the user needs to run ansi2knr. Currently, this is not supported, so we just abort.

aphostname
    From d_gethname.U:

    Thie variable contains the command which can be used to compute the host name. The command is fully qualified by its absolute path, to make it safe when used by a process with super-user privileges.

apiversion
    From patchlevel.U:

    This is a number which identifies the lowest version of perl to have an API (for XS extensions) compatible with the present version. For example, for 5.005_01, the apiversion should be 5.005, since 5.005_01 should be binary compatible with 5.005. This should probably be incremented manually somehow, perhaps from patchlevel.h. For now, we'll guess maintenance subversions will retain binary compatibility.

ar  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the ar program. After Configure runs, the value is reset to a plain ar and is not useful.

archlib
    From archlib.U:

    This variable holds the name of the directory in which the user wants to put architecture-dependent public library files for $package. It is most often a local directory such as /usr/local/lib. Programs using this variable must be prepared to deal with filename expansion.

archlibexp
    From archlib.U:

    This variable is the same as the archlib variable, but is filename expanded at configuration time, for convenient use.

archname
    From archname.U:

    This variable is a short name to characterize the current architecture. It is used mainly to construct the default archlib.

archobjs
    From Unix.U:

    This variable defines any additional objects that must be linked in with the program on this architecture. On unix, it is usually empty. It is typically used to include emulations of unix calls or other facilities. For perl on OS/2, for example, this would include os2/os2.obj.

awk From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the awk program. After Configure runs, the value is reset to a plain awk and is not useful.

  b

baserev
    From baserev.U:

    The base revision level of this package, from the .package file.

bash
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

bin From bin.U:

    This variable holds the name of the directory in which the user wants to put publicly executable images for the package in question. It is most often a local directory such as /usr/local/bin. Programs using this variable must be prepared to deal with ~name substitution.

binexp
    From bin.U:

    This is the same as the bin variable, but is filename expanded at configuration time, for use in your makefiles.

bison
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

byacc
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the byacc program. After Configure runs, the value is reset to a plain byacc and is not useful.

byteorder
    From byteorder.U:

    This variable holds the byte order. In the following, larger digits indicate more significance. The variable byteorder is either 4321 on a big-endian machine, or 1234 on a little-endian, or 87654321 on a Cray ... or 3412 with weird order !

  c

c   From n.U:

    This variable contains the \c string if that is what causes the echo command to suppress newline. Otherwise it is null. Correct usage is

            $echo $n "prompt for a question: $c".

castflags
    From d_castneg.U:

    This variable contains a flag that precise difficulties the compiler has casting odd floating values to unsigned long:

            0 = ok
            1 = couldn't cast < 0
            2 = couldn't cast >= 0x80000000
            4 = couldn't cast in argument expression list

cat From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the cat program. After Configure runs, the value is reset to a plain cat and is not useful.

cc  From cc.U:

    This variable holds the name of a command to execute a C compiler which can resolve multiple global references that happen to have the same name. Usual values are cc, Mcc, cc -M, and gcc.

cccdlflags
    From dlsrc.U:

    This variable contains any special flags that might need to be passed with cc -c to compile modules to be used to create a shared library that will be used for dynamic loading. For hpux, this should be +z. It is up to the makefile to use it.

ccdlflags
    From dlsrc.U:

    This variable contains any special flags that might need to be passed to cc to link with a shared library for dynamic loading. It is up to the makefile to use it. For sunos 4.1, it should be empty.

ccflags
    From ccflags.U:

    This variable contains any additional C compiler flags desired by the user. It is up to the Makefile to use this.

ccsymbols
    From Cppsym.U:

    The variable contains the symbols defined by the C compiler alone. The symbols defined by cpp or by cc when it calls cpp are not in this list, see cppsymbols and cppccsymbols. The list is a space-separated list of symbol=value tokens.

cf_by
    From cf_who.U:

    Login name of the person who ran the Configure script and answered the questions. This is used to tag both config.sh and config_h.SH.

cf_email
    From cf_email.U:

    Electronic mail address of the person who ran Configure. This can be used by units that require the user's e-mail, like MailList.U.

cf_time
    From cf_who.U:

    Holds the output of the date command when the configuration file was produced. This is used to tag both config.sh and config_h.SH.

chgrp
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

chmod
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

chown
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

clocktype
    From d_times.U:

    This variable holds the type returned by times(). It can be long, or clock_t on BSD sites (in which case <sys/types.h> should be included).

comm
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the comm program. After Configure runs, the value is reset to a plain comm and is not useful.

compress
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

contains
    From contains.U:

    This variable holds the command to do a grep with a proper return status. On most sane systems it is simply grep. On insane systems it is a grep followed by a cat followed by a test. This variable is primarily for the use of other Configure units.

cp  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the cp program. After Configure runs, the value is reset to a plain cp and is not useful.

cpio
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

cpp From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the cpp program. After Configure runs, the value is reset to a plain cpp and is not useful.

cpp_stuff
    From cpp_stuff.U:

    This variable contains an identification of the catenation mechanism used by the C preprocessor.

cppflags
    From ccflags.U:

    This variable holds the flags that will be passed to the C pre- processor. It is up to the Makefile to use it.

cpplast
    From cppstdin.U:

    This variable has the same functionality as cppminus, only it applies to cpprun and not cppstdin.

cppminus
    From cppstdin.U:

    This variable contains the second part of the string which will invoke the C preprocessor on the standard input and produce to standard output. This variable will have the value - if cppstdin needs a minus to specify standard input, otherwise the value is "".

cpprun
    From cppstdin.U:

    This variable contains the command which will invoke a C preprocessor on standard input and put the output to stdout. It is guaranteed not to be a wrapper and may be a null string if no preprocessor can be made directly available. This preprocessor might be different from the one used by the C compiler. Don't forget to append cpplast after the preprocessor options.

cppstdin
    From cppstdin.U:

    This variable contains the command which will invoke the C preprocessor on standard input and put the output to stdout. It is primarily used by other Configure units that ask about preprocessor symbols.

cppsymbols
    From Cppsym.U:

    The variable contains the symbols defined by the C preprocessor alone. The symbols defined by cc or by cc when it calls cpp are not in this list, see ccsymbols and cppccsymbols. The list is a space-separated list of symbol=value tokens.

cppccsymbols
    From Cppsym.U:

    The variable contains the symbols defined by the C compiler when when it calls cpp. The symbols defined by the cc alone or cpp alone are not in this list, see ccsymbols and cppsymbols. The list is a space-separated list of symbol=value tokens.

cryptlib
    From d_crypt.U:

    This variable holds -lcrypt or the path to a libcrypt.a archive if the crypt() function is not defined in the standard C library. It is up to the Makefile to use this.

csh From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the csh program. After Configure runs, the value is reset to a plain csh and is not useful.

  d

d_Gconvert
    From d_gconvert.U:

    This variable holds what Gconvert is defined as to convert floating point numbers into strings. It could be gconvert or a more complex macro emulating gconvert with gcvt() or sprintf.

d_access
    From d_access.U:

    This variable conditionally defines HAS_ACCESS if the access() system call is available to check for access permissions using real IDs.

d_alarm
    From d_alarm.U:

    This variable conditionally defines the HAS_ALARM symbol, which indicates to the C program that the alarm() routine is available.

d_archlib
    From archlib.U:

    This variable conditionally defines ARCHLIB to hold the pathname of architecture-dependent library files for $package. If $archlib is the same as $privlib, then this is set to undef.

d_attribut
    From d_attribut.U:

    This variable conditionally defines HASATTRIBUTE, which indicates the C compiler can check for function attributes, such as printf formats.

d_bcmp
    From d_bcmp.U:

    This variable conditionally defines the HAS_BCMP symbol if the bcmp() routine is available to compare strings.

d_bcopy
    From d_bcopy.U:

    This variable conditionally defines the HAS_BCOPY symbol if the bcopy() routine is available to copy strings.

d_bsd
    From Guess.U:

    This symbol conditionally defines the symbol BSD when running on a BSD system.

d_bsdgetpgrp
    From d_getpgrp.U:

    This variable conditionally defines USE_BSD_GETPGRP if getpgrp needs one arguments whereas USG one needs none.

d_bsdsetpgrp
    From d_setpgrp.U:

    This variable conditionally defines USE_BSD_SETPGRP if setpgrp needs two arguments whereas USG one needs none. See also d_setpgid for a POSIX interface.

d_bzero
    From d_bzero.U:

    This variable conditionally defines the HAS_BZERO symbol if the bzero() routine is available to set memory to 0.

d_casti32
    From d_casti32.U:

    This variable conditionally defines CASTI32, which indicates whether the C compiler can cast large floats to 32-bit ints.

d_castneg
    From d_castneg.U:

    This variable conditionally defines CASTNEG, which indicates wether the C compiler can cast negative float to unsigned.

d_charvspr
    From d_vprintf.U:

    This variable conditionally defines CHARVSPRINTF if this system has vsprintf returning type (char*). The trend seems to be to declare it as "int vsprintf()".

d_chown
    From d_chown.U:

    This variable conditionally defines the HAS_CHOWN symbol, which indicates to the C program that the chown() routine is available.

d_chroot
    From d_chroot.U:

    This variable conditionally defines the HAS_CHROOT symbol, which indicates to the C program that the chroot() routine is available.

d_chsize
    From d_chsize.U:

    This variable conditionally defines the CHSIZE symbol, which indicates to the C program that the chsize() routine is available to truncate files. You might need a -lx to get this routine.

d_closedir
    From d_closedir.U:

    This variable conditionally defines HAS_CLOSEDIR if closedir() is available.

d_const
    From d_const.U:

    This variable conditionally defines the HASCONST symbol, which indicates to the C program that this C compiler knows about the const type.

d_crypt
    From d_crypt.U:

    This variable conditionally defines the CRYPT symbol, which indicates to the C program that the crypt() routine is available to encrypt passwords and the like.

d_csh
    From d_csh.U:

    This variable conditionally defines the CSH symbol, which indicates to the C program that the C-shell exists.

d_cuserid
    From d_cuserid.U:

    This variable conditionally defines the HAS_CUSERID symbol, which indicates to the C program that the cuserid() routine is available to get character login names.

d_dbl_dig
    From d_dbl_dig.U:

    This variable conditionally defines d_dbl_dig if this system's header files provide DBL_DIG, which is the number of significant digits in a double precision number.

d_difftime
    From d_difftime.U:

    This variable conditionally defines the HAS_DIFFTIME symbol, which indicates to the C program that the difftime() routine is available.

d_dirnamlen
    From i_dirent.U:

    This variable conditionally defines DIRNAMLEN, which indicates to the C program that the length of directory entry names is provided by a d_namelen field.

d_dlerror
    From d_dlerror.U:

    This variable conditionally defines the HAS_DLERROR symbol, which indicates to the C program that the dlerror() routine is available.

d_dlopen
    From d_dlopen.U:

    This variable conditionally defines the HAS_DLOPEN symbol, which indicates to the C program that the dlopen() routine is available.

d_dlsymun
    From d_dlsymun.U:

    This variable conditionally defines DLSYM_NEEDS_UNDERSCORE, which indicates that we need to prepend an underscore to the symbol name before calling dlsym().

d_dosuid
    From d_dosuid.U:

    This variable conditionally defines the symbol DOSUID, which tells the C program that it should insert setuid emulation code on hosts which have setuid #! scripts disabled.

d_dup2
    From d_dup2.U:

    This variable conditionally defines HAS_DUP2 if dup2() is available to duplicate file descriptors.

d_endgrent
    From d_endgrent.U:

    This variable conditionally defines the HAS_ENDGRENT symbol, which indicates to the C program that the endgrent() routine is available for sequential access of the group database.

d_endhent
    From d_endhent.U:

    This variable conditionally defines HAS_ENDHOSTENT if endhostent() is available to close whatever was being used for host queries.

d_endnent
    From d_endnent.U:

    This variable conditionally defines HAS_ENDNETENT if endnetent() is available to close whatever was being used for network queries.

d_endpent
    From d_endpent.U:

    This variable conditionally defines HAS_ENDPROTOENT if endprotoent() is available to close whatever was being used for protocol queries.

d_endpwent
    From d_endpwent.U:

    This variable conditionally defines the HAS_ENDPWENT symbol, which indicates to the C program that the endpwent() routine is available for sequential access of the passwd database.

d_endsent
    From d_endsent.U:

    This variable conditionally defines HAS_ENDSERVENT if endservent() is available to close whatever was being used for service queries.

d_eofnblk
    From nblock_io.U:

    This variable conditionally defines EOF_NONBLOCK if EOF can be seen when reading from a non-blocking I/O source.

d_eunice
    From Guess.U:

    This variable conditionally defines the symbols EUNICE and VAX, which alerts the C program that it must deal with ideosyncracies of VMS.

d_fchmod
    From d_fchmod.U:

    This variable conditionally defines the HAS_FCHMOD symbol, which indicates to the C program that the fchmod() routine is available to change mode of opened files.

d_fchown
    From d_fchown.U:

    This variable conditionally defines the HAS_FCHOWN symbol, which indicates to the C program that the fchown() routine is available to change ownership of opened files.

d_fcntl
    From d_fcntl.U:

    This variable conditionally defines the HAS_FCNTL symbol, and indicates whether the fcntl() function exists

d_fd_macros
    From d_fd_set.U:

    This variable contains the eventual value of the HAS_FD_MACROS symbol, which indicates if your C compiler knows about the macros which manipulate an fd_set.

d_fd_set
    From d_fd_set.U:

    This variable contains the eventual value of the HAS_FD_SET symbol, which indicates if your C compiler knows about the fd_set typedef.

d_fds_bits
    From d_fd_set.U:

    This variable contains the eventual value of the HAS_FDS_BITS symbol, which indicates if your fd_set typedef contains the fds_bits member. If you have an fd_set typedef, but the dweebs who installed it did a half-fast job and neglected to provide the macros to manipulate an fd_set, HAS_FDS_BITS will let us know how to fix the gaffe.

d_fgetpos
    From d_fgetpos.U:

    This variable conditionally defines HAS_FGETPOS if fgetpos() is available to get the file position indicator.

d_flexfnam
    From d_flexfnam.U:

    This variable conditionally defines the FLEXFILENAMES symbol, which indicates that the system supports filenames longer than 14 characters.

d_flock
    From d_flock.U:

    This variable conditionally defines HAS_FLOCK if flock() is available to do file locking.

d_fork
    From d_fork.U:

    This variable conditionally defines the HAS_FORK symbol, which indicates to the C program that the fork() routine is available.

d_fpathconf
    From d_pathconf.U:

    This variable conditionally defines the HAS_FPATHCONF symbol, which indicates to the C program that the pathconf() routine is available to determine file-system related limits and options associated with a given open file descriptor.

d_fsetpos
    From d_fsetpos.U:

    This variable conditionally defines HAS_FSETPOS if fsetpos() is available to set the file position indicator.

d_fstatfs
    From d_statfs.U:

    This variable conditionally defines the HAS_FSTATFS symbol, which indicates to the C program that the fstatfs() routine is available.

d_fstatvfs
    From d_statvfs.U:

    This variable conditionally defines the HAS_FSTATVFS symbol, which indicates to the C program that the fstatvfs() routine is available.

d_ftime
    From d_ftime.U:

    This variable conditionally defines the HAS_FTIME symbol, which indicates that the ftime() routine exists. The ftime() routine is basically a sub-second accuracy clock.

d_getgrent
    From d_getgrent.U:

    This variable conditionally defines the HAS_GETGRENT symbol, which indicates to the C program that the getgrent() routine is available for sequential access of the group database.

d_getgrps
    From d_getgrps.U:

    This variable conditionally defines the HAS_GETGROUPS symbol, which indicates to the C program that the getgroups() routine is available to get the list of process groups.

d_gethbyaddr
    From d_gethbyad.U:

    This variable conditionally defines the HAS_GETHOSTBYADDR symbol, which indicates to the C program that the gethostbyaddr() routine is available to look up hosts by their IP addresses.

d_gethbyname
    From d_gethbynm.U:

    This variable conditionally defines the HAS_GETHOSTBYNAME symbol, which indicates to the C program that the gethostbyname() routine is available to look up host names in some data base or other.

d_gethent
    From d_gethent.U:

    This variable conditionally defines HAS_GETHOSTENT if gethostent() is available to look up host names in some data base or another.

d_gethname
    From d_gethname.U:

    This variable conditionally defines the HAS_GETHOSTNAME symbol, which indicates to the C program that the gethostname() routine may be used to derive the host name.

d_gethostprotos
    From d_gethostprotos.U:

    This variable conditionally defines the HAS_GETHOST_PROTOS symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various gethost*() functions. See also netdbtype.U for probing for various netdb types.

d_getlogin
    From d_getlogin.U:

    This variable conditionally defines the HAS_GETLOGIN symbol, which indicates to the C program that the getlogin() routine is available to get the login name.

d_getmntent
    From d_getmntent.U:

    This variable conditionally defines the HAS_GETMNTENT symbol, which indicates to the C program that the getmntent() routine is available to iterate through mounted files.

d_getnbyaddr
    From d_getnbyad.U:

    This variable conditionally defines the HAS_GETNETBYADDR symbol, which indicates to the C program that the getnetbyaddr() routine is available to look up networks by their IP addresses.

d_getnbyname
    From d_getnbynm.U:

    This variable conditionally defines the HAS_GETNETBYNAME symbol, which indicates to the C program that the getnetbyname() routine is available to look up networks by their names.

d_getnent
    From d_getnent.U:

    This variable conditionally defines HAS_GETNETENT if getnetent() is available to look up network names in some data base or another.

d_getnetprotos
    From d_getnetprotos.U:

    This variable conditionally defines the HAS_GETNET_PROTOS symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various getnet*() functions. See also netdbtype.U for probing for various netdb types.

d_getpbyname
    From d_getprotby.U:

    This variable conditionally defines the HAS_GETPROTOBYNAME symbol, which indicates to the C program that the getprotobyname() routine is available to look up protocols by their name.

d_getpbynumber
    From d_getprotby.U:

    This variable conditionally defines the HAS_GETPROTOBYNUMBER symbol, which indicates to the C program that the getprotobynumber() routine is available to look up protocols by their number.

d_getpent
    From d_getpent.U:

    This variable conditionally defines HAS_GETPROTOENT if getprotoent() is available to look up protocols in some data base or another.

d_getpgid
    From d_getpgid.U:

    This variable conditionally defines the HAS_GETPGID symbol, which indicates to the C program that the getpgid(pid) function is available to get the process group id.

d_getpgrp2
    From d_getpgrp2.U:

    This variable conditionally defines the HAS_GETPGRP2 symbol, which indicates to the C program that the getpgrp2() (as in DG/UX) routine is available to get the current process group.

d_getpgrp
    From d_getpgrp.U:

    This variable conditionally defines HAS_GETPGRP if getpgrp() is available to get the current process group.

d_getppid
    From d_getppid.U:

    This variable conditionally defines the HAS_GETPPID symbol, which indicates to the C program that the getppid() routine is available to get the parent process ID.

d_getprior
    From d_getprior.U:

    This variable conditionally defines HAS_GETPRIORITY if getpriority() is available to get a process's priority.

d_getprotoprotos
    From d_getprotoprotos.U:

    This variable conditionally defines the HAS_GETPROTO_PROTOS symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various getproto*() functions. See also netdbtype.U for probing for various netdb types.

d_getpwent
    From d_getpwent.U:

    This variable conditionally defines the HAS_GETPWENT symbol, which indicates to the C program that the getpwent() routine is available for sequential access of the passwd database.

d_getsbyname
    From d_getsrvby.U:

    This variable conditionally defines the HAS_GETSERVBYNAME symbol, which indicates to the C program that the getservbyname() routine is available to look up services by their name.

d_getsbyport
    From d_getsrvby.U:

    This variable conditionally defines the HAS_GETSERVBYPORT symbol, which indicates to the C program that the getservbyport() routine is available to look up services by their port.

d_getsent
    From d_getsent.U:

    This variable conditionally defines HAS_GETSERVENT if getservent() is available to look up network services in some data base or another.

d_getservprotos
    From d_getservprotos.U:

    This variable conditionally defines the HAS_GETSERV_PROTOS symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various getserv*() functions. See also netdbtype.U for probing for various netdb types.

d_gettimeod
    From d_ftime.U:

    This variable conditionally defines the HAS_GETTIMEOFDAY symbol, which indicates that the gettimeofday() system call exists (to obtain a sub-second accuracy clock). You should probably include <sys/resource.h>.

d_gnulibc
    From d_gnulibc.U:

    Defined if we're dealing with the GNU C Library.

d_grpasswd
    From i_grp.U:

    This variable conditionally defines GRPASSWD, which indicates that struct group in <grp.h> contains gr_passwd.

d_hasmntopt
    From d_hasmntopt.U:

    This variable conditionally defines the HAS_HASMNTOPT symbol, which indicates to the C program that the hasmntopt() routine is available to query the mount options of file systems.

d_htonl
    From d_htonl.U:

    This variable conditionally defines HAS_HTONL if htonl() and its friends are available to do network order byte swapping.

d_index
    From d_strchr.U:

    This variable conditionally defines HAS_INDEX if index() and rindex() are available for string searching.

d_inetaton
    From d_inetaton.U:

    This variable conditionally defines the HAS_INET_ATON symbol, which indicates to the C program that the inet_aton() function is available to parse IP address dotted-quad strings.

d_isascii
    From d_isascii.U:

    This variable conditionally defines the HAS_ISASCII constant, which indicates to the C program that isascii() is available.

d_killpg
    From d_killpg.U:

    This variable conditionally defines the HAS_KILLPG symbol, which indicates to the C program that the killpg() routine is available to kill process groups.

d_lchown
    From d_lchown.U:

    This variable conditionally defines the HAS_LCHOWN symbol, which indicates to the C program that the lchown() routine is available to operate on a symbolic link (instead of following the link).

d_link
    From d_link.U:

    This variable conditionally defines HAS_LINK if link() is available to create hard links.

d_locconv
    From d_locconv.U:

    This variable conditionally defines HAS_LOCALECONV if localeconv() is available for numeric and monetary formatting conventions.

d_lockf
    From d_lockf.U:

    This variable conditionally defines HAS_LOCKF if lockf() is available to do file locking.

d_longdbl
    From d_longdbl.U:

    This variable conditionally defines HAS_LONG_DOUBLE if the long double type is supported.

d_longlong
    From d_longlong.U:

    This variable conditionally defines HAS_LONG_LONG if the long long type is supported.

d_lstat
    From d_lstat.U:

    This variable conditionally defines HAS_LSTAT if lstat() is available to do file stats on symbolic links.

d_mblen
    From d_mblen.U:

    This variable conditionally defines the HAS_MBLEN symbol, which indicates to the C program that the mblen() routine is available to find the number of bytes in a multibye character.

d_mbstowcs
    From d_mbstowcs.U:

    This variable conditionally defines the HAS_MBSTOWCS symbol, which indicates to the C program that the mbstowcs() routine is available to convert a multibyte string into a wide character string.

d_mbtowc
    From d_mbtowc.U:

    This variable conditionally defines the HAS_MBTOWC symbol, which indicates to the C program that the mbtowc() routine is available to convert multibyte to a wide character.

d_memcmp
    From d_memcmp.U:

    This variable conditionally defines the HAS_MEMCMP symbol, which indicates to the C program that the memcmp() routine is available to compare blocks of memory.

d_memcpy
    From d_memcpy.U:

    This variable conditionally defines the HAS_MEMCPY symbol, which indicates to the C program that the memcpy() routine is available to copy blocks of memory.

d_memmove
    From d_memmove.U:

    This variable conditionally defines the HAS_MEMMOVE symbol, which indicates to the C program that the memmove() routine is available to copy potentatially overlapping blocks of memory.

d_memset
    From d_memset.U:

    This variable conditionally defines the HAS_MEMSET symbol, which indicates to the C program that the memset() routine is available to set blocks of memory.

d_mkdir
    From d_mkdir.U:

    This variable conditionally defines the HAS_MKDIR symbol, which indicates to the C program that the mkdir() routine is available to create directories..

d_mkfifo
    From d_mkfifo.U:

    This variable conditionally defines the HAS_MKFIFO symbol, which indicates to the C program that the mkfifo() routine is available.

d_mktime
    From d_mktime.U:

    This variable conditionally defines the HAS_MKTIME symbol, which indicates to the C program that the mktime() routine is available.

d_msg
    From d_msg.U:

    This variable conditionally defines the HAS_MSG symbol, which indicates that the entire msg*(2) library is present.

d_msgctl
    From d_msgctl.U:

    This variable conditionally defines the HAS_MSGCTL symbol, which indicates to the C program that the msgctl() routine is available.

d_msgget
    From d_msgget.U:

    This variable conditionally defines the HAS_MSGGET symbol, which indicates to the C program that the msgget() routine is available.

d_msgrcv
    From d_msgrcv.U:

    This variable conditionally defines the HAS_MSGRCV symbol, which indicates to the C program that the msgrcv() routine is available.

d_msgsnd
    From d_msgsnd.U:

    This variable conditionally defines the HAS_MSGSND symbol, which indicates to the C program that the msgsnd() routine is available.

d_mymalloc
    From mallocsrc.U:

    This variable conditionally defines MYMALLOC in case other parts of the source want to take special action if MYMALLOC is used. This may include different sorts of profiling or error detection.

d_nice
    From d_nice.U:

    This variable conditionally defines the HAS_NICE symbol, which indicates to the C program that the nice() routine is available.

d_oldpthreads
    From usethreads.U:

    This variable conditionally defines the OLD_PTHREADS_API symbol, and indicates that Perl should be built to use the old draft POSIX threads API. This is only potneially meaningful if usethreads is set.

d_oldsock
    From d_socket.U:

    This variable conditionally defines the OLDSOCKET symbol, which indicates that the BSD socket interface is based on 4.1c and not 4.2.

d_open3
    From d_open3.U:

    This variable conditionally defines the HAS_OPEN3 manifest constant, which indicates to the C program that the 3 argument version of the open(2) function is available.

d_pathconf
    From d_pathconf.U:

    This variable conditionally defines the HAS_PATHCONF symbol, which indicates to the C program that the pathconf() routine is available to determine file-system related limits and options associated with a given filename.

d_pause
    From d_pause.U:

    This variable conditionally defines the HAS_PAUSE symbol, which indicates to the C program that the pause() routine is available to suspend a process until a signal is received.

d_phostname
    From d_gethname.U:

    This variable conditionally defines the PHOSTNAME symbol, which contains the shell command which, when fed to popen(), may be used to derive the host name.

d_pipe
    From d_pipe.U:

    This variable conditionally defines the HAS_PIPE symbol, which indicates to the C program that the pipe() routine is available to create an inter-process channel.

d_poll
    From d_poll.U:

    This variable conditionally defines the HAS_POLL symbol, which indicates to the C program that the poll() routine is available to poll active file descriptors.

d_portable
    From d_portable.U:

    This variable conditionally defines the PORTABLE symbol, which indicates to the C program that it should not assume that it is running on the machine it was compiled on.

d_pthread_yield
    From d_pthread_y.U:

    This variable conditionally defines the HAS_PTHREAD_YIELD symbol if the pthread_yield routine is available to yield the execution of the current thread.

d_pthreads_created_joinable
    From d_pthreadj.U:

    This variable conditionally defines the PTHREADS_CREATED_JOINABLE symbol if pthreads are created in the joinable (aka undetached) state.

d_pwage
    From i_pwd.U:

    This variable conditionally defines PWAGE, which indicates that struct passwd contains pw_age.

d_pwchange
    From i_pwd.U:

    This variable conditionally defines PWCHANGE, which indicates that struct passwd contains pw_change.

d_pwclass
    From i_pwd.U:

    This variable conditionally defines PWCLASS, which indicates that struct passwd contains pw_class.

d_pwcomment
    From i_pwd.U:

    This variable conditionally defines PWCOMMENT, which indicates that struct passwd contains pw_comment.

d_pwexpire
    From i_pwd.U:

    This variable conditionally defines PWEXPIRE, which indicates that struct passwd contains pw_expire.

d_pwgecos
    From i_pwd.U:

    This variable conditionally defines PWGECOS, which indicates that struct passwd contains pw_gecos.

d_pwpasswd
    From i_pwd.U:

    This variable conditionally defines PWPASSWD, which indicates that struct passwd contains pw_passwd.

d_pwquota
    From i_pwd.U:

    This variable conditionally defines PWQUOTA, which indicates that struct passwd contains pw_quota.

d_readdir
    From d_readdir.U:

    This variable conditionally defines HAS_READDIR if readdir() is available to read directory entries.

d_readlink
    From d_readlink.U:

    This variable conditionally defines the HAS_READLINK symbol, which indicates to the C program that the readlink() routine is available to read the value of a symbolic link.

d_rename
    From d_rename.U:

    This variable conditionally defines the HAS_RENAME symbol, which indicates to the C program that the rename() routine is available to rename files.

d_rewinddir
    From d_readdir.U:

    This variable conditionally defines HAS_REWINDDIR if rewinddir() is available.

d_rmdir
    From d_rmdir.U:

    This variable conditionally defines HAS_RMDIR if rmdir() is available to remove directories.

d_safebcpy
    From d_safebcpy.U:

    This variable conditionally defines the HAS_SAFE_BCOPY symbol if the bcopy() routine can do overlapping copies.

d_safemcpy
    From d_safemcpy.U:

    This variable conditionally defines the HAS_SAFE_MEMCPY symbol if the memcpy() routine can do overlapping copies.

d_sanemcmp
    From d_sanemcmp.U:

    This variable conditionally defines the HAS_SANE_MEMCMP symbol if the memcpy() routine is available and can be used to compare relative magnitudes of chars with their high bits set.

d_sched_yield
    From d_pthread_y.U:

    This variable conditionally defines the HAS_SCHED_YIELD symbol if the sched_yield routine is available to yield the execution of the current thread.

d_seekdir
    From d_readdir.U:

    This variable conditionally defines HAS_SEEKDIR if seekdir() is available.

d_select
    From d_select.U:

    This variable conditionally defines HAS_SELECT if select() is available to select active file descriptors. A <sys/time.h> inclusion may be necessary for the timeout field.

d_sem
    From d_sem.U:

    This variable conditionally defines the HAS_SEM symbol, which indicates that the entire sem*(2) library is present.

d_semctl
    From d_semctl.U:

    This variable conditionally defines the HAS_SEMCTL symbol, which indicates to the C program that the semctl() routine is available.

d_semctl_semid_ds
    From d_union_senum.U:

    This variable conditionally defines USE_SEMCTL_SEMID_DS, which indicates that struct semid_ds * is to be used for semctl IPC_STAT.

d_semctl_semun
    From d_union_senum.U:

    This variable conditionally defines USE_SEMCTL_SEMUN, which indicates that union semun is to be used for semctl IPC_STAT.

d_semget
    From d_semget.U:

    This variable conditionally defines the HAS_SEMGET symbol, which indicates to the C program that the semget() routine is available.

d_semop
    From d_semop.U:

    This variable conditionally defines the HAS_SEMOP symbol, which indicates to the C program that the semop() routine is available.

d_setegid
    From d_setegid.U:

    This variable conditionally defines the HAS_SETEGID symbol, which indicates to the C program that the setegid() routine is available to change the effective gid of the current program.

d_seteuid
    From d_seteuid.U:

    This variable conditionally defines the HAS_SETEUID symbol, which indicates to the C program that the seteuid() routine is available to change the effective uid of the current program.

d_setgrent
    From d_setgrent.U:

    This variable conditionally defines the HAS_SETGRENT symbol, which indicates to the C program that the setgrent() routine is available for initializing sequential access to the group database.

d_setgrps
    From d_setgrps.U:

    This variable conditionally defines the HAS_SETGROUPS symbol, which indicates to the C program that the setgroups() routine is available to set the list of process groups.

d_sethent
    From d_sethent.U:

    This variable conditionally defines HAS_SETHOSTENT if sethostent() is available.

d_setlinebuf
    From d_setlnbuf.U:

    This variable conditionally defines the HAS_SETLINEBUF symbol, which indicates to the C program that the setlinebuf() routine is available to change stderr or stdout from block-buffered or unbuffered to a line-buffered mode.

d_setlocale
    From d_setlocale.U:

    This variable conditionally defines HAS_SETLOCALE if setlocale() is available to handle locale-specific ctype implementations.

d_setnent
    From d_setnent.U:

    This variable conditionally defines HAS_SETNETENT if setnetent() is available.

d_setpent
    From d_setpent.U:

    This variable conditionally defines HAS_SETPROTOENT if setprotoent() is available.

d_setpgid
    From d_setpgid.U:

    This variable conditionally defines the HAS_SETPGID symbol if the setpgid(pid, gpid) function is available to set process group ID.

d_setpgrp2
    From d_setpgrp2.U:

    This variable conditionally defines the HAS_SETPGRP2 symbol, which indicates to the C program that the setpgrp2() (as in DG/UX) routine is available to set the current process group.

d_setpgrp
    From d_setpgrp.U:

    This variable conditionally defines HAS_SETPGRP if setpgrp() is available to set the current process group.

d_setprior
    From d_setprior.U:

    This variable conditionally defines HAS_SETPRIORITY if setpriority() is available to set a process's priority.

d_setpwent
    From d_setpwent.U:

    This variable conditionally defines the HAS_SETPWENT symbol, which indicates to the C program that the setpwent() routine is available for initializing sequential access to the passwd database.

d_setregid
    From d_setregid.U:

    This variable conditionally defines HAS_SETREGID if setregid() is available to change the real and effective gid of the current process.

d_setresgid
    From d_setregid.U:

    This variable conditionally defines HAS_SETRESGID if setresgid() is available to change the real, effective and saved gid of the current process.

d_setresuid
    From d_setreuid.U:

    This variable conditionally defines HAS_SETREUID if setresuid() is available to change the real, effective and saved uid of the current process.

d_setreuid
    From d_setreuid.U:

    This variable conditionally defines HAS_SETREUID if setreuid() is available to change the real and effective uid of the current process.

d_setrgid
    From d_setrgid.U:

    This variable conditionally defines the HAS_SETRGID symbol, which indicates to the C program that the setrgid() routine is available to change the real gid of the current program.

d_setruid
    From d_setruid.U:

    This variable conditionally defines the HAS_SETRUID symbol, which indicates to the C program that the setruid() routine is available to change the real uid of the current program.

d_setsent
    From d_setsent.U:

    This variable conditionally defines HAS_SETSERVENT if setservent() is available.

d_setsid
    From d_setsid.U:

    This variable conditionally defines HAS_SETSID if setsid() is available to set the process group ID.

d_setvbuf
    From d_setvbuf.U:

    This variable conditionally defines the HAS_SETVBUF symbol, which indicates to the C program that the setvbuf() routine is available to change buffering on an open stdio stream.

d_sfio
    From d_sfio.U:

    This variable conditionally defines the USE_SFIO symbol, and indicates whether sfio is available (and should be used).

d_shm
    From d_shm.U:

    This variable conditionally defines the HAS_SHM symbol, which indicates that the entire shm*(2) library is present.

d_shmat
    From d_shmat.U:

    This variable conditionally defines the HAS_SHMAT symbol, which indicates to the C program that the shmat() routine is available.

d_shmatprototype
    From d_shmat.U:

    This variable conditionally defines the HAS_SHMAT_PROTOTYPE symbol, which indicates that sys/shm.h has a prototype for shmat.

d_shmctl
    From d_shmctl.U:

    This variable conditionally defines the HAS_SHMCTL symbol, which indicates to the C program that the shmctl() routine is available.

d_shmdt
    From d_shmdt.U:

    This variable conditionally defines the HAS_SHMDT symbol, which indicates to the C program that the shmdt() routine is available.

d_shmget
    From d_shmget.U:

    This variable conditionally defines the HAS_SHMGET symbol, which indicates to the C program that the shmget() routine is available.

d_sigaction
    From d_sigaction.U:

    This variable conditionally defines the HAS_SIGACTION symbol, which indicates that the Vr4 sigaction() routine is available.

d_sigsetjmp
    From d_sigsetjmp.U:

    This variable conditionally defines the HAS_SIGSETJMP symbol, which indicates that the sigsetjmp() routine is available to call setjmp() and optionally save the process's signal mask.

d_socket
    From d_socket.U:

    This variable conditionally defines HAS_SOCKET, which indicates that the BSD socket interface is supported.

d_sockpair
    From d_socket.U:

    This variable conditionally defines the HAS_SOCKETPAIR symbol, which indicates that the BSD socketpair() is supported.

d_statblks
    From d_statblks.U:

    This variable conditionally defines USE_STAT_BLOCKS if this system has a stat structure declaring st_blksize and st_blocks.

d_statfsflags
    From d_statfs.U:

    This variable conditionally defines the HAS_STRUCT_STATFS_FLAGS symbol, which indicates to struct statfs from has f_flags member. This kind of struct statfs is coming from sys/mount.h (BSD), not from sys/statfs.h (SYSV).

d_statvfs
    From d_statvfs.U:

    This variable conditionally defines the HAS_STATVFS symbol, which indicates to the C program that the statvfs() routine is available.

d_stdio_cnt_lval
    From d_stdstdio.U:

    This variable conditionally defines STDIO_CNT_LVALUE if the FILE_cnt macro can be used as an lvalue.

d_stdio_ptr_lval
    From d_stdstdio.U:

    This variable conditionally defines STDIO_PTR_LVALUE if the FILE_ptr macro can be used as an lvalue.

d_stdiobase
    From d_stdstdio.U:

    This variable conditionally defines USE_STDIO_BASE if this system has a FILE structure declaring a usable _base field (or equivalent) in stdio.h.

d_stdstdio
    From d_stdstdio.U:

    This variable conditionally defines USE_STDIO_PTR if this system has a FILE structure declaring usable _ptr and _cnt fields (or equivalent) in stdio.h.

d_strchr
    From d_strchr.U:

    This variable conditionally defines HAS_STRCHR if strchr() and strrchr() are available for string searching.

d_strcoll
    From d_strcoll.U:

    This variable conditionally defines HAS_STRCOLL if strcoll() is available to compare strings using collating information.

d_strctcpy
    From d_strctcpy.U:

    This variable conditionally defines the USE_STRUCT_COPY symbol, which indicates to the C program that this C compiler knows how to copy structures.

d_strerrm
    From d_strerror.U:

    This variable holds what Strerrr is defined as to translate an error code condition into an error message string. It could be strerror or a more complex macro emulating strrror with sys_errlist[], or the unknown string when both strerror and sys_errlist are missing.

d_strerror
    From d_strerror.U:

    This variable conditionally defines HAS_STRERROR if strerror() is available to translate error numbers to strings.

d_strtod
    From d_strtod.U:

    This variable conditionally defines the HAS_STRTOD symbol, which indicates to the C program that the strtod() routine is available to provide better numeric string conversion than atof().

d_strtol
    From d_strtol.U:

    This variable conditionally defines the HAS_STRTOL symbol, which indicates to the C program that the strtol() routine is available to provide better numeric string conversion than atoi() and friends.

d_strtoul
    From d_strtoul.U:

    This variable conditionally defines the HAS_STRTOUL symbol, which indicates to the C program that the strtoul() routine is available to provide conversion of strings to unsigned long.

d_strxfrm
    From d_strxfrm.U:

    This variable conditionally defines HAS_STRXFRM if strxfrm() is available to transform strings.

d_suidsafe
    From d_dosuid.U:

    This variable conditionally defines SETUID_SCRIPTS_ARE_SECURE_NOW if setuid scripts can be secure. This test looks in /dev/fd/.

d_symlink
    From d_symlink.U:

    This variable conditionally defines the HAS_SYMLINK symbol, which indicates to the C program that the symlink() routine is available to create symbolic links.

d_syscall
    From d_syscall.U:

    This variable conditionally defines HAS_SYSCALL if syscall() is available call arbitrary system calls.

d_sysconf
    From d_sysconf.U:

    This variable conditionally defines the HAS_SYSCONF symbol, which indicates to the C program that the sysconf() routine is available to determine system related limits and options.

d_sysernlst
    From d_strerror.U:

    This variable conditionally defines HAS_SYS_ERRNOLIST if sys_errnolist[] is available to translate error numbers to the symbolic name.

d_syserrlst
    From d_strerror.U:

    This variable conditionally defines HAS_SYS_ERRLIST if sys_errlist[] is available to translate error numbers to strings.

d_system
    From d_system.U:

    This variable conditionally defines HAS_SYSTEM if system() is available to issue a shell command.

d_tcgetpgrp
    From d_tcgtpgrp.U:

    This variable conditionally defines the HAS_TCGETPGRP symbol, which indicates to the C program that the tcgetpgrp() routine is available. to get foreground process group ID.

d_tcsetpgrp
    From d_tcstpgrp.U:

    This variable conditionally defines the HAS_TCSETPGRP symbol, which indicates to the C program that the tcsetpgrp() routine is available to set foreground process group ID.

d_telldir
    From d_readdir.U:

    This variable conditionally defines HAS_TELLDIR if telldir() is available.

d_time
    From d_time.U:

    This variable conditionally defines the HAS_TIME symbol, which indicates that the time() routine exists. The time() routine is normaly provided on UNIX systems.

d_times
    From d_times.U:

    This variable conditionally defines the HAS_TIMES symbol, which indicates that the times() routine exists. The times() routine is normaly provided on UNIX systems. You may have to include <sys/times.h>.

d_truncate
    From d_truncate.U:

    This variable conditionally defines HAS_TRUNCATE if truncate() is available to truncate files.

d_tzname
    From d_tzname.U:

    This variable conditionally defines HAS_TZNAME if tzname[] is available to access timezone names.

d_umask
    From d_umask.U:

    This variable conditionally defines the HAS_UMASK symbol, which indicates to the C program that the umask() routine is available. to set and get the value of the file creation mask.

d_uname
    From d_gethname.U:

    This variable conditionally defines the HAS_UNAME symbol, which indicates to the C program that the uname() routine may be used to derive the host name.

d_union_semun
    From d_union_senum.U:

    This variable conditionally defines HAS_UNION_SEMUN if the union semun is defined by including <sys/sem.h>.

d_vfork
    From d_vfork.U:

    This variable conditionally defines the HAS_VFORK symbol, which indicates the vfork() routine is available.

d_void_closedir
    From d_closedir.U:

    This variable conditionally defines VOID_CLOSEDIR if closedir() does not return a value.

d_voidsig
    From d_voidsig.U:

    This variable conditionally defines VOIDSIG if this system declares "void (*signal(...))()" in signal.h. The old way was to declare it as "int (*signal(...))()".

d_voidtty
    From i_sysioctl.U:

    This variable conditionally defines USE_IOCNOTTY to indicate that the ioctl() call with TIOCNOTTY should be used to void tty association. Otherwise (on USG probably), it is enough to close the standard file decriptors and do a setpgrp().

d_volatile
    From d_volatile.U:

    This variable conditionally defines the HASVOLATILE symbol, which indicates to the C program that this C compiler knows about the volatile declaration.

d_vprintf
    From d_vprintf.U:

    This variable conditionally defines the HAS_VPRINTF symbol, which indicates to the C program that the vprintf() routine is available to printf with a pointer to an argument list.

d_wait4
    From d_wait4.U:

    This variable conditionally defines the HAS_WAIT4 symbol, which indicates the wait4() routine is available.

d_waitpid
    From d_waitpid.U:

    This variable conditionally defines HAS_WAITPID if waitpid() is available to wait for child process.

d_wcstombs
    From d_wcstombs.U:

    This variable conditionally defines the HAS_WCSTOMBS symbol, which indicates to the C program that the wcstombs() routine is available to convert wide character strings to multibyte strings.

d_wctomb
    From d_wctomb.U:

    This variable conditionally defines the HAS_WCTOMB symbol, which indicates to the C program that the wctomb() routine is available to convert a wide character to a multibyte.

d_xenix
    From Guess.U:

    This variable conditionally defines the symbol XENIX, which alerts the C program that it runs under Xenix.

date
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the date program. After Configure runs, the value is reset to a plain date and is not useful.

db_hashtype
    From i_db.U:

    This variable contains the type of the hash structure element in the <db.h> header file. In older versions of DB, it was int, while in newer ones it is u_int32_t.

db_prefixtype
    From i_db.U:

    This variable contains the type of the prefix structure element in the <db.h> header file. In older versions of DB, it was int, while in newer ones it is size_t.

direntrytype
    From i_dirent.U:

    This symbol is set to struct direct or struct dirent depending on whether dirent is available or not. You should use this pseudo type to portably declare your directory entries.

dlext
    From dlext.U:

    This variable contains the extension that is to be used for the dynamically loaded modules that perl generaties.

dlsrc
    From dlsrc.U:

    This variable contains the name of the dynamic loading file that will be used with the package.

doublesize
    From doublesize.U:

    This variable contains the value of the DOUBLESIZE symbol, which indicates to the C program how many bytes there are in a double.

dynamic_ext
    From Extensions.U:

    This variable holds a list of XS extension files we want to link dynamically into the package. It is used by Makefile.

  e

eagain
    From nblock_io.U:

    This variable bears the symbolic errno code set by read() when no data is present on the file and non-blocking I/O was enabled (otherwise, read() blocks naturally).

ebcdic
    From ebcdic.U:

    This variable conditionally defines EBCDIC if this system uses EBCDIC encoding. Among other things, this means that the character ranges are not contiguous. See trnl.U

echo
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the echo program. After Configure runs, the value is reset to a plain echo and is not useful.

egrep
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the egrep program. After Configure runs, the value is reset to a plain egrep and is not useful.

emacs
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

eunicefix
    From Init.U:

    When running under Eunice this variable contains a command which will convert a shell script to the proper form of text file for it to be executable by the shell. On other systems it is a no-op.

exe_ext
    From Unix.U:

    This is an old synonym for _exe.

expr
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the expr program. After Configure runs, the value is reset to a plain expr and is not useful.

extensions
    From Extensions.U:

    This variable holds a list of all extension files (both XS and non-xs linked into the package. It is propagated to Config.pm and is typically used to test whether a particular extesion is available.

  f

find
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the find program. After Configure runs, the value is reset to a plain find and is not useful.

firstmakefile
    From Unix.U:

    This variable defines the first file searched by make. On unix, it is makefile (then Makefile). On case-insensitive systems, it might be something else. This is only used to deal with convoluted make depend tricks.

flex
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

fpostype
    From fpostype.U:

    This variable defines Fpos_t to be something like fpost_t, long, uint, or whatever type is used to declare file positions in libc.

freetype
    From mallocsrc.U:

    This variable contains the return type of free(). It is usually void, but occasionally int.

full_ar
    From Loc_ar.U:

    This variable contains the full pathname to ar, whether or not the user has specified portability. This is only used in the Makefile.SH.

full_csh
    From d_csh.U:

    This variable contains the full pathname to csh, whether or not the user has specified portability. This is only used in the compiled C program, and we assume that all systems which can share this executable will have the same full pathname to csh.

full_sed
    From Loc_sed.U:

    This variable contains the full pathname to sed, whether or not the user has specified portability. This is only used in the compiled C program, and we assume that all systems which can share this executable will have the same full pathname to sed.

  g

gccversion
    From cc.U:

    If GNU cc (gcc) is used, this variable holds 1 or 2 to indicate whether the compiler is version 1 or 2. This is used in setting some of the default cflags. It is set to '' if not gcc.

gidtype
    From gidtype.U:

    This variable defines Gid_t to be something like gid_t, int, ushort, or whatever type is used to declare the return type of getgid(). Typically, it is the type of group ids in the kernel.

grep
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the grep program. After Configure runs, the value is reset to a plain grep and is not useful.

groupcat
    From nis.U:

    This variable contains a command that produces the text of the /etc/group file. This is normally "cat /etc/group", but can be "ypcat group" when NIS is used.

groupstype
    From groupstype.U:

    This variable defines Groups_t to be something like gid_t, int, ushort, or whatever type is used for the second argument to getgroups() and setgroups(). Usually, this is the same as gidtype (gid_t), but sometimes it isn't.

gzip
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the gzip program. After Configure runs, the value is reset to a plain gzip and is not useful.

  h

h_fcntl
    From h_fcntl.U:

    This is variable gets set in various places to tell i_fcntl that <fcntl.h> should be included.

h_sysfile
    From h_sysfile.U:

    This is variable gets set in various places to tell i_sys_file that <sys/file.h> should be included.

hint
    From Oldconfig.U:

    Gives the type of hints used for previous answers. May be one of default, recommended or previous.

hostcat
    From nis.U:

    This variable contains a command that produces the text of the /etc/hosts file. This is normally "cat /etc/hosts", but can be "ypcat hosts" when NIS is used.

huge
    From models.U:

    This variable contains a flag which will tell the C compiler and loader to produce a program running with a huge memory model. If the huge model is not supported, contains the flag to produce large model programs. It is up to the Makefile to use this.

  i

i_arpainet
    From i_arpainet.U:

    This variable conditionally defines the I_ARPA_INET symbol, and indicates whether a C program should include <arpa/inet.h>.

i_bsdioctl
    From i_sysioctl.U:

    This variable conditionally defines the I_SYS_BSDIOCTL symbol, which indicates to the C program that <sys/bsdioctl.h> exists and should be included.

i_db
    From i_db.U:

    This variable conditionally defines the I_DB symbol, and indicates whether a C program may include Berkeley's DB include file <db.h>.

i_dbm
    From i_dbm.U:

    This variable conditionally defines the I_DBM symbol, which indicates to the C program that <dbm.h> exists and should be included.

i_dirent
    From i_dirent.U:

    This variable conditionally defines I_DIRENT, which indicates to the C program that it should include <dirent.h>.

i_dld
    From i_dld.U:

    This variable conditionally defines the I_DLD symbol, which indicates to the C program that <dld.h> (GNU dynamic loading) exists and should be included.

i_dlfcn
    From i_dlfcn.U:

    This variable conditionally defines the I_DLFCN symbol, which indicates to the C program that <dlfcn.h> exists and should be included.

i_fcntl
    From i_fcntl.U:

    This variable controls the value of I_FCNTL (which tells the C program to include <fcntl.h>).

i_float
    From i_float.U:

    This variable conditionally defines the I_FLOAT symbol, and indicates whether a C program may include <float.h> to get symbols like DBL_MAX or DBL_MIN, i.e. machine dependent floating point values.

i_gdbm
    From i_gdbm.U:

    This variable conditionally defines the I_GDBM symbol, which indicates to the C program that <gdbm.h> exists and should be included.

i_grp
    From i_grp.U:

    This variable conditionally defines the I_GRP symbol, and indicates whether a C program should include <grp.h>.

i_limits
    From i_limits.U:

    This variable conditionally defines the I_LIMITS symbol, and indicates whether a C program may include <limits.h> to get symbols like WORD_BIT and friends.

i_locale
    From i_locale.U:

    This variable conditionally defines the I_LOCALE symbol, and indicates whether a C program should include <locale.h>.

i_machcthr
    From i_machcthr.U:

    This variable conditionally defines the I_MACH_CTHREADS symbol, and indicates whether a C program should include <mach/cthreads.h>.

i_malloc
    From i_malloc.U:

    This variable conditionally defines the I_MALLOC symbol, and indicates whether a C program should include <malloc.h>.

i_math
    From i_math.U:

    This variable conditionally defines the I_MATH symbol, and indicates whether a C program may include <math.h>.

i_memory
    From i_memory.U:

    This variable conditionally defines the I_MEMORY symbol, and indicates whether a C program should include <memory.h>.

i_mntent
    From i_mntent.U:

    This variable conditionally defines the I_MNTENT symbol, and indicates whether a C program should include <mntent.h>.

i_ndbm
    From i_ndbm.U:

    This variable conditionally defines the I_NDBM symbol, which indicates to the C program that <ndbm.h> exists and should be included.

i_netdb
    From i_netdb.U:

    This variable conditionally defines the I_NETDB symbol, and indicates whether a C program should include <netdb.h>.

i_neterrno
    From i_neterrno.U:

    This variable conditionally defines the I_NET_ERRNO symbol, which indicates to the C program that <net/errno.h> exists and should be included.

i_niin
    From i_niin.U:

    This variable conditionally defines I_NETINET_IN, which indicates to the C program that it should include <netinet/in.h>. Otherwise, you may try <sys/in.h>.

i_pwd
    From i_pwd.U:

    This variable conditionally defines I_PWD, which indicates to the C program that it should include <pwd.h>.

i_rpcsvcdbm
    From i_dbm.U:

    This variable conditionally defines the I_RPCSVC_DBM symbol, which indicates to the C program that <rpcsvc/dbm.h> exists and should be included. Some System V systems might need this instead of <dbm.h>.

i_sfio
    From i_sfio.U:

    This variable conditionally defines the I_SFIO symbol, and indicates whether a C program should include <sfio.h>.

i_sgtty
    From i_termio.U:

    This variable conditionally defines the I_SGTTY symbol, which indicates to the C program that it should include <sgtty.h> rather than <termio.h>.

i_stdarg
    From i_varhdr.U:

    This variable conditionally defines the I_STDARG symbol, which indicates to the C program that <stdarg.h> exists and should be included.

i_stddef
    From i_stddef.U:

    This variable conditionally defines the I_STDDEF symbol, which indicates to the C program that <stddef.h> exists and should be included.

i_stdlib
    From i_stdlib.U:

    This variable conditionally defines the I_STDLIB symbol, which indicates to the C program that <stdlib.h> exists and should be included.

i_string
    From i_string.U:

    This variable conditionally defines the I_STRING symbol, which indicates that <string.h> should be included rather than <strings.h>.

i_sysdir
    From i_sysdir.U:

    This variable conditionally defines the I_SYS_DIR symbol, and indicates whether a C program should include <sys/dir.h>.

i_sysfile
    From i_sysfile.U:

    This variable conditionally defines the I_SYS_FILE symbol, and indicates whether a C program should include <sys/file.h> to get R_OK and friends.

i_sysfilio
    From i_sysioctl.U:

    This variable conditionally defines the I_SYS_FILIO symbol, which indicates to the C program that <sys/filio.h> exists and should be included in preference to <sys/ioctl.h>.

i_sysin
    From i_niin.U:

    This variable conditionally defines I_SYS_IN, which indicates to the C program that it should include <sys/in.h> instead of <netinet/in.h>.

i_sysioctl
    From i_sysioctl.U:

    This variable conditionally defines the I_SYS_IOCTL symbol, which indicates to the C program that <sys/ioctl.h> exists and should be included.

i_sysmount
    From i_sysmount.U:

    This variable conditionally defines the I_SYSMOUNT symbol, and indicates whether a C program should include <sys/mount.h>.

i_sysndir
    From i_sysndir.U:

    This variable conditionally defines the I_SYS_NDIR symbol, and indicates whether a C program should include <sys/ndir.h>.

i_sysparam
    From i_sysparam.U:

    This variable conditionally defines the I_SYS_PARAM symbol, and indicates whether a C program should include <sys/param.h>.

i_sysresrc
    From i_sysresrc.U:

    This variable conditionally defines the I_SYS_RESOURCE symbol, and indicates whether a C program should include <sys/resource.h>.

i_sysselct
    From i_sysselct.U:

    This variable conditionally defines I_SYS_SELECT, which indicates to the C program that it should include <sys/select.h> in order to get the definition of struct timeval.

i_syssockio
    From i_sysioctl.U:

    This variable conditionally defines I_SYS_SOCKIO to indicate to the C program that socket ioctl codes may be found in <sys/sockio.h> instead of <sys/ioctl.h>.

i_sysstat
    From i_sysstat.U:

    This variable conditionally defines the I_SYS_STAT symbol, and indicates whether a C program should include <sys/stat.h>.

i_sysstatfs
    From i_sysstatfs.U:

    This variable conditionally defines the I_SYSSTATFS symbol, and indicates whether a C program should include <sys/statfs.h>.

i_sysstatvfs
    From i_sysstatvfs.U:

    This variable conditionally defines the I_SYSSTATVFS symbol, and indicates whether a C program should include <sys/statvfs.h>.

i_systime
    From i_time.U:

    This variable conditionally defines I_SYS_TIME, which indicates to the C program that it should include <sys/time.h>.

i_systimek
    From i_time.U:

    This variable conditionally defines I_SYS_TIME_KERNEL, which indicates to the C program that it should include <sys/time.h> with KERNEL defined.

i_systimes
    From i_systimes.U:

    This variable conditionally defines the I_SYS_TIMES symbol, and indicates whether a C program should include <sys/times.h>.

i_systypes
    From i_systypes.U:

    This variable conditionally defines the I_SYS_TYPES symbol, and indicates whether a C program should include <sys/types.h>.

i_sysun
    From i_sysun.U:

    This variable conditionally defines I_SYS_UN, which indicates to the C program that it should include <sys/un.h> to get UNIX domain socket definitions.

i_syswait
    From i_syswait.U:

    This variable conditionally defines I_SYS_WAIT, which indicates to the C program that it should include <sys/wait.h>.

i_termio
    From i_termio.U:

    This variable conditionally defines the I_TERMIO symbol, which indicates to the C program that it should include <termio.h> rather than <sgtty.h>.

i_termios
    From i_termio.U:

    This variable conditionally defines the I_TERMIOS symbol, which indicates to the C program that the POSIX <termios.h> file is to be included.

i_time
    From i_time.U:

    This variable conditionally defines I_TIME, which indicates to the C program that it should include <time.h>.

i_unistd
    From i_unistd.U:

    This variable conditionally defines the I_UNISTD symbol, and indicates whether a C program should include <unistd.h>.

i_utime
    From i_utime.U:

    This variable conditionally defines the I_UTIME symbol, and indicates whether a C program should include <utime.h>.

i_values
    From i_values.U:

    This variable conditionally defines the I_VALUES symbol, and indicates whether a C program may include <values.h> to get symbols like MAXLONG and friends.

i_varargs
    From i_varhdr.U:

    This variable conditionally defines I_VARARGS, which indicates to the C program that it should include <varargs.h>.

i_varhdr
    From i_varhdr.U:

    Contains the name of the header to be included to get va_dcl definition. Typically one of varargs.h or stdarg.h.

i_vfork
    From i_vfork.U:

    This variable conditionally defines the I_VFORK symbol, and indicates whether a C program should include vfork.h.

ignore_versioned_solibs
    From libs.U:

    This variable should be non-empty if non-versioned shared libraries (libfoo.so.x.y) are to be ignored (because they cannot be linked against).

incpath
    From usrinc.U:

    This variable must preceed the normal include path to get hte right one, as in $incpath/usr/include or $incpath/usr/lib. Value can be "" or /bsd43 on mips.

inews
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

installarchlib
    From archlib.U:

    This variable is really the same as archlibexp but may differ on those systems using AFS. For extra portability, only this variable should be used in makefiles.

installbin
    From bin.U:

    This variable is the same as binexp unless AFS is running in which case the user is explicitely prompted for it. This variable should always be used in your makefiles for maximum portability.

installman1dir
    From man1dir.U:

    This variable is really the same as man1direxp, unless you are using AFS in which case it points to the read/write location whereas man1direxp only points to the read-only access location. For extra portability, you should only use this variable within your makefiles.

installman3dir
    From man3dir.U:

    This variable is really the same as man3direxp, unless you are using AFS in which case it points to the read/write location whereas man3direxp only points to the read-only access location. For extra portability, you should only use this variable within your makefiles.

installprivlib
    From privlib.U:

    This variable is really the same as privlibexp but may differ on those systems using AFS. For extra portability, only this variable should be used in makefiles.

installscript
    From scriptdir.U:

    This variable is usually the same as scriptdirexp, unless you are on a system running AFS, in which case they may differ slightly. You should always use this variable within your makefiles for portability.

installsitearch
    From sitearch.U:

    This variable is really the same as sitearchexp but may differ on those systems using AFS. For extra portability, only this variable should be used in makefiles.

installsitelib
    From sitelib.U:

    This variable is really the same as sitelibexp but may differ on those systems using AFS. For extra portability, only this variable should be used in makefiles.

installusrbinperl
    From instubperl.U:

    This variable tells whether Perl should be installed also as /usr/bin/perl in addition to $installbin/perl

intsize
    From intsize.U:

    This variable contains the value of the INTSIZE symbol, which indicates to the C program how many bytes there are in an int.

  k

known_extensions
    From Extensions.U:

    This variable holds a list of all XS extensions included in the package.

ksh From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

  l

large
    From models.U:

    This variable contains a flag which will tell the C compiler and loader to produce a program running with a large memory model. It is up to the Makefile to use this.

ld  From dlsrc.U:

    This variable indicates the program to be used to link libraries for dynamic loading. On some systems, it is ld. On ELF systems, it should be $cc. Mostly, we'll try to respect the hint file setting.

lddlflags
    From dlsrc.U:

    This variable contains any special flags that might need to be passed to $ld to create a shared library suitable for dynamic loading. It is up to the makefile to use it. For hpux, it should be -b. For sunos 4.1, it is empty.

ldflags
    From ccflags.U:

    This variable contains any additional C loader flags desired by the user. It is up to the Makefile to use this.

less
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the less program. After Configure runs, the value is reset to a plain less and is not useful.

lib_ext
    From Unix.U:

    This is an old synonym for _a.

libc
    From libc.U:

    This variable contains the location of the C library.

libperl
    From libperl.U:

    The perl executable is obtained by linking perlmain.c with libperl, any static extensions (usually just DynaLoader), and any other libraries needed on this system. libperl is usually libperl.a, but can also be libperl.so.xxx if the user wishes to build a perl executable with a shared library.

libpth
    From libpth.U:

    This variable holds the general path used to find libraries. It is intended to be used by other units.

libs
    From libs.U:

    This variable holds the additional libraries we want to use. It is up to the Makefile to deal with it.

libswanted
    From Myinit.U:

    This variable holds a list of all the libraries we want to search. The order is chosen to pick up the c library ahead of ucb or bsd libraries for SVR4.

line
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the line program. After Configure runs, the value is reset to a plain line and is not useful.

lint
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

lkflags
    From ccflags.U:

    This variable contains any additional C partial linker flags desired by the user. It is up to the Makefile to use this.

ln  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the ln program. After Configure runs, the value is reset to a plain ln and is not useful.

lns From lns.U:

    This variable holds the name of the command to make symbolic links (if they are supported). It can be used in the Makefile. It is either ln -s or ln

locincpth
    From ccflags.U:

    This variable contains a list of additional directories to be searched by the compiler. The appropriate -I directives will be added to ccflags. This is intended to simplify setting local directories from the Configure command line. It's not much, but it parallels the loclibpth stuff in libpth.U.

loclibpth
    From libpth.U:

    This variable holds the paths used to find local libraries. It is prepended to libpth, and is intended to be easily set from the command line.

longdblsize
    From d_longdbl.U:

    This variable contains the value of the LONG_DOUBLESIZE symbol, which indicates to the C program how many bytes there are in a long double, if this system supports long doubles.

longlongsize
    From d_longlong.U:

    This variable contains the value of the LONGLONGSIZE symbol, which indicates to the C program how many bytes there are in a long long, if this system supports long long.

longsize
    From intsize.U:

    This variable contains the value of the LONGSIZE symbol, which indicates to the C program how many bytes there are in a long.

lp  From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

lpr From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

ls  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the ls program. After Configure runs, the value is reset to a plain ls and is not useful.

lseektype
    From lseektype.U:

    This variable defines lseektype to be something like off_t, long, or whatever type is used to declare lseek offset's type in the kernel (which also appears to be lseek's return type).

  m

mail
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

mailx
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

make
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the make program. After Configure runs, the value is reset to a plain make and is not useful.

make_set_make
    From make.U:

    Some versions of make set the variable MAKE. Others do not. This variable contains the string to be included in Makefile.SH so that MAKE is set if needed, and not if not needed. Possible values are:
    make_set_make=#    # If your make program handles this for you,
    make_set_make=MAKE=$make    # if it doesn't.
    I used a comment character so that we can distinguish a set value (from a previous config.sh or Configure -D option) from an uncomputed value.

mallocobj
    From mallocsrc.U:

    This variable contains the name of the malloc.o that this package generates, if that malloc.o is preferred over the system malloc. Otherwise the value is null. This variable is intended for generating Makefiles. See mallocsrc.

mallocsrc
    From mallocsrc.U:

    This variable contains the name of the malloc.c that comes with the package, if that malloc.c is preferred over the system malloc. Otherwise the value is null. This variable is intended for generating Makefiles.

malloctype
    From mallocsrc.U:

    This variable contains the kind of ptr returned by malloc and realloc.

man1dir
    From man1dir.U:

    This variable contains the name of the directory in which manual source pages are to be put. It is the responsibility of the Makefile.SH to get the value of this into the proper command. You must be prepared to do the ~name expansion yourself.

man1direxp
    From man1dir.U:

    This variable is the same as the man1dir variable, but is filename expanded at configuration time, for convenient use in makefiles.

man1ext
    From man1dir.U:

    This variable contains the extension that the manual page should have: one of n, l, or 1. The Makefile must supply the .. See man1dir.

man3dir
    From man3dir.U:

    This variable contains the name of the directory in which manual source pages are to be put. It is the responsibility of the Makefile.SH to get the value of this into the proper command. You must be prepared to do the ~name expansion yourself.

man3direxp
    From man3dir.U:

    This variable is the same as the man3dir variable, but is filename expanded at configuration time, for convenient use in makefiles.

man3ext
    From man3dir.U:

    This variable contains the extension that the manual page should have: one of n, l, or 3. The Makefile must supply the .. See man3dir.

medium
    From models.U:

    This variable contains a flag which will tell the C compiler and loader to produce a program running with a medium memory model. If the medium model is not supported, contains the flag to produce large model programs. It is up to the Makefile to use this.

mips_type
    From usrinc.U:

    This variable holds the environment type for the mips system. Possible values are "BSD 4.3" and "System V".

mkdir
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the mkdir program. After Configure runs, the value is reset to a plain mkdir and is not useful.

models
    From models.U:

    This variable contains the list of memory models supported by this system. Possible component values are none, split, unsplit, small, medium, large, and huge. The component values are space separated.

modetype
    From modetype.U:

    This variable defines modetype to be something like mode_t, int, unsigned short, or whatever type is used to declare file modes for system calls.

more
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the more program. After Configure runs, the value is reset to a plain more and is not useful.

mv  From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

myarchname
    From archname.U:

    This variable holds the architecture name computed by Configure in a previous run. It is not intended to be perused by any user and should never be set in a hint file.

mydomain
    From myhostname.U:

    This variable contains the eventual value of the MYDOMAIN symbol, which is the domain of the host the program is going to run on. The domain must be appended to myhostname to form a complete host name. The dot comes with mydomain, and need not be supplied by the program.

myhostname
    From myhostname.U:

    This variable contains the eventual value of the MYHOSTNAME symbol, which is the name of the host the program is going to run on. The domain is not kept with hostname, but must be gotten from mydomain. The dot comes with mydomain, and need not be supplied by the program.

myuname
    From Oldconfig.U:

    The output of uname -a if available, otherwise the hostname. On Xenix, pseudo variables assignments in the output are stripped, thank you. The whole thing is then lower-cased.

  n

n   From n.U:

    This variable contains the -n flag if that is what causes the echo command to suppress newline. Otherwise it is null. Correct usage is

            $echo $n "prompt for a question: $c".

netdb_hlen_type
    From netdbtype.U:

    This variable holds the type used for the 2nd argument to gethostbyaddr(). Usually, this is int or size_t or unsigned. This is only useful if you have gethostbyaddr(), naturally.

netdb_host_type
    From netdbtype.U:

    This variable holds the type used for the 1st argument to gethostbyaddr(). Usually, this is char * or void *, possibly with or without a const prefix. This is only useful if you have gethostbyaddr(), naturally.

netdb_name_type
    From netdbtype.U:

    This variable holds the type used for the argument to gethostbyname(). Usually, this is char * or const char *. This is only useful if you have gethostbyname(), naturally.

netdb_net_type
    From netdbtype.U:

    This variable holds the type used for the 1st argument to getnetbyaddr(). Usually, this is int or long. This is only useful if you have getnetbyaddr(), naturally.

nm  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the nm program. After Configure runs, the value is reset to a plain nm and is not useful.

nm_opt
    From usenm.U:

    This variable holds the options that may be necessary for nm.

nm_so_opt
    From usenm.U:

    This variable holds the options that may be necessary for nm to work on a shared library but that can not be used on an archive library. Currently, this is only used by Linux, where nm --dynamic is *required* to get symbols from an ELF library which has been stripped, but nm --dynamic is *fatal* on an archive library. Maybe Linux should just always set usenm=false.

nonxs_ext
    From Extensions.U:

    This variable holds a list of all non-xs extensions included in the package. All of them will be built.

nroff
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the nroff program. After Configure runs, the value is reset to a plain nroff and is not useful.

  o

o_nonblock
    From nblock_io.U:

    This variable bears the symbol value to be used during open() or fcntl() to turn on non-blocking I/O for a file descriptor. If you wish to switch between blocking and non-blocking, you may try ioctl(FIOSNBIO) instead, but that is only supported by some devices.

obj_ext
    From Unix.U:

    This is an old synonym for _o.

optimize
    From ccflags.U:

    This variable contains any optimizer/debugger flag that should be used. It is up to the Makefile to use it.

orderlib
    From orderlib.U:

    This variable is true if the components of libraries must be ordered (with `lorder $* | tsort`) before placing them in an archive. Set to false if ranlib or ar can generate random libraries.

osname
    From Oldconfig.U:

    This variable contains the operating system name (e.g. sunos, solaris, hpux, etc.). It can be useful later on for setting defaults. Any spaces are replaced with underscores. It is set to a null string if we can't figure it out.

osvers
    From Oldconfig.U:

    This variable contains the operating system version (e.g. 4.1.3, 5.2, etc.). It is primarily used for helping select an appropriate hints file, but might be useful elsewhere for setting defaults. It is set to '' if we can't figure it out. We try to be flexible about how much of the version number to keep, e.g. if 4.1.1, 4.1.2, and 4.1.3 are essentially the same for this package, hints files might just be os_4.0 or os_4.1, etc., not keeping separate files for each little release.

  p

package
    From package.U:

    This variable contains the name of the package being constructed. It is primarily intended for the use of later Configure units.

pager
    From pager.U:

    This variable contains the name of the preferred pager on the system. Usual values are (the full pathnames of) more, less, pg, or cat.

passcat
    From nis.U:

    This variable contains a command that produces the text of the /etc/passwd file. This is normally "cat /etc/passwd", but can be "ypcat passwd" when NIS is used.

patchlevel
    From patchlevel.U:

    The patchlevel level of this package. The value of patchlevel comes from the patchlevel.h file.

path_sep
    From Unix.U:

    This is an old synonym for p_ in Head.U, the character used to separate elements in the command shell search PATH.

perl
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the perl program. After Configure runs, the value is reset to a plain perl and is not useful.

perladmin
    From perladmin.U:

    Electronic mail address of the perl5 administrator.

perlpath
    From perlpath.U:

    This variable contains the eventual value of the PERLPATH symbol, which contains the name of the perl interpreter to be used in shell scripts and in the "eval exec" idiom.

pg  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the pg program. After Configure runs, the value is reset to a plain pg and is not useful.

phostname
    From myhostname.U:

    This variable contains the eventual value of the PHOSTNAME symbol, which is a command that can be fed to popen() to get the host name. The program should probably not presume that the domain is or isn't there already.

pidtype
    From pidtype.U:

    This variable defines PIDTYPE to be something like pid_t, int, ushort, or whatever type is used to declare process ids in the kernel.

plibpth
    From libpth.U:

    Holds the private path used by Configure to find out the libraries. Its value is prepend to libpth. This variable takes care of special machines, like the mips. Usually, it should be empty.

pmake
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

pr  From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

prefix
    From prefix.U:

    This variable holds the name of the directory below which the user will install the package. Usually, this is /usr/local, and executables go in /usr/local/bin, library stuff in /usr/local/lib, man pages in /usr/local/man, etc. It is only used to set defaults for things in bin.U, mansrc.U, privlib.U, or scriptdir.U.

prefixexp
    From prefix.U:

    This variable holds the full absolute path of the directory below which the user will install the package. Derived from prefix.

privlib
    From privlib.U:

    This variable contains the eventual value of the PRIVLIB symbol, which is the name of the private library for this package. It may have a ~ on the front. It is up to the makefile to eventually create this directory while performing installation (with ~ substitution).

privlibexp
    From privlib.U:

    This variable is the ~name expanded version of privlib, so that you may use it directly in Makefiles or shell scripts.

prototype
    From prototype.U:

    This variable holds the eventual value of CAN_PROTOTYPE, which indicates the C compiler can handle funciton prototypes.

ptrsize
    From ptrsize.U:

    This variable contains the value of the PTRSIZE symbol, which indicates to the C program how many bytes there are in a pointer.

  r

randbits
    From randbits.U:

    This variable contains the eventual value of the RANDBITS symbol, which indicates to the C program how many bits of random number the rand() function produces.

ranlib
    From orderlib.U:

    This variable is set to the pathname of the ranlib program, if it is needed to generate random libraries. Set to : if ar can generate random libraries or if random libraries are not supported

rd_nodata
    From nblock_io.U:

    This variable holds the return code from read() when no data is present. It should be -1, but some systems return 0 when O_NDELAY is used, which is a shame because you cannot make the difference between no data and an EOF.. Sigh!

rm  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the rm program. After Configure runs, the value is reset to a plain rm and is not useful.

rmail
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

runnm
    From usenm.U:

    This variable contains true or false depending whether the nm extraction should be performed or not, according to the value of usenm and the flags on the Configure command line.

  s

scriptdir
    From scriptdir.U:

    This variable holds the name of the directory in which the user wants to put publicly scripts for the package in question. It is either the same directory as for binaries, or a special one that can be mounted across different architectures, like /usr/share. Programs must be prepared to deal with ~name expansion.

scriptdirexp
    From scriptdir.U:

    This variable is the same as scriptdir, but is filename expanded at configuration time, for programs not wanting to bother with it.

sed From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the sed program. After Configure runs, the value is reset to a plain sed and is not useful.

selectminbits
    From selectminbits.U:

    This variable holds the minimum number of bits operated by select. That is, if you do select(n, ...), how many bits at least will be cleared in the masks if some activity is detected. Usually this is either n or 32*ceil(n/32), especially many little-endians do the latter. This is only useful if you have select(), naturally.

selecttype
    From selecttype.U:

    This variable holds the type used for the 2nd, 3rd, and 4th arguments to select. Usually, this is fd_set *, if HAS_FD_SET is defined, and int * otherwise. This is only useful if you have select(), naturally.

sendmail
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the sendmail program. After Configure runs, the value is reset to a plain sendmail and is not useful.

sh  From sh.U:

    This variable contains the full pathname of the shell used on this system to execute Bourne shell scripts. Usually, this will be /bin/sh, though it's possible that some systems will have /bin/ksh, /bin/pdksh, /bin/ash, /bin/bash, or even something such as D:/bin/sh.exe. This unit comes before Options.U, so you can't set sh with a -D option, though you can override this (and startsh) with -O -Dsh=/bin/whatever -Dstartsh=whatever

shar
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

sharpbang
    From spitshell.U:

    This variable contains the string #! if this system supports that construct.

shmattype
    From d_shmat.U:

    This symbol contains the type of pointer returned by shmat(). It can be void * or char *.

shortsize
    From intsize.U:

    This variable contains the value of the SHORTSIZE symbol which indicates to the C program how many bytes there are in a short.

shrpenv
    From libperl.U:

    If the user builds a shared libperl.so, then we need to tell the perl executable where it will be able to find the installed libperl.so. One way to do this on some systems is to set the environment variable LD_RUN_PATH to the directory that will be the final location of the shared libperl.so. The makefile can use this with something like

            $shrpenv $(C<CC>) -o perl F<perlmain.o> $libperl $libs
            Typical values are
            shrpenv="env C<LD_RUN_PATH>=$F<archlibexp/C<CORE>>"
            or
            shrpenv=''
            See the main perl F<Makefile.SH> for actual working usage.
    Alternatively, we might be able to use a command line option such
    as -R $F<archlibexp/C<CORE>> (Solaris, NetBSD) or -Wl,-rpath
    $F<archlibexp/C<CORE>> (Linux).

shsharp
    From spitshell.U:

    This variable tells further Configure units whether your sh can handle # comments.

sig_name
    From sig_name.U:

    This variable holds the signal names, space separated. The leading SIG in signal name is removed. A ZERO is prepended to the list. This is currently not used.

sig_name_init
    From sig_name.U:

    This variable holds the signal names, enclosed in double quotes and separated by commas, suitable for use in the SIG_NAME definition below. A ZERO is prepended to the list, and the list is terminated with a plain 0. The leading SIG in signal names is removed. See sig_num.

sig_num
    From sig_name.U:

    This variable holds the signal numbers, comma separated. A 0 is prepended to the list (corresponding to the fake SIGZERO), and the list is terminated with a 0. Those numbers correspond to the value of the signal listed in the same place within the sig_name list.

sig_num_init
    From sig_name.U:

    This variable holds the signal numbers, enclosed in double quotes and separated by commas, suitable for use in the SIG_NUM definition below. A ZERO is prepended to the list, and the list is terminated with a plain 0.

signal_t
    From d_voidsig.U:

    This variable holds the type of the signal handler (void or int).

sitearch
    From sitearch.U:

    This variable contains the eventual value of the SITEARCH symbol, which is the name of the private library for this package. It may have a ~ on the front. It is up to the makefile to eventually create this directory while performing installation (with ~ substitution).

sitearchexp
    From sitearch.U:

    This variable is the ~name expanded version of sitearch, so that you may use it directly in Makefiles or shell scripts.

sitelib
    From sitelib.U:

    This variable contains the eventual value of the SITELIB symbol, which is the name of the private library for this package. It may have a ~ on the front. It is up to the makefile to eventually create this directory while performing installation (with ~ substitution).

sitelibexp
    From sitelib.U:

    This variable is the ~name expanded version of sitelib, so that you may use it directly in Makefiles or shell scripts.

sizetype
    From sizetype.U:

    This variable defines sizetype to be something like size_t, unsigned long, or whatever type is used to declare length parameters for string functions.

sleep
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

smail
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

small
    From models.U:

    This variable contains a flag which will tell the C compiler and loader to produce a program running with a small memory model. It is up to the Makefile to use this.

so  From so.U:

    This variable holds the extension used to identify shared libraries (also known as shared objects) on the system. Usually set to so.

sockethdr
    From d_socket.U:

    This variable has any cpp -I flags needed for socket support.

socketlib
    From d_socket.U:

    This variable has the names of any libraries needed for socket support.

sort
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the sort program. After Configure runs, the value is reset to a plain sort and is not useful.

spackage
    From package.U:

    This variable contains the name of the package being constructed, with the first letter uppercased, i.e. suitable for starting sentences.

spitshell
    From spitshell.U:

    This variable contains the command necessary to spit out a runnable shell on this system. It is either cat or a grep -v for # comments.

split
    From models.U:

    This variable contains a flag which will tell the C compiler and loader to produce a program that will run in separate I and D space, for those machines that support separation of instruction and data space. It is up to the Makefile to use this.

src From src.U:

    This variable holds the path to the package source. It is up to the Makefile to use this variable and set VPATH accordingly to find the sources remotely.

ssizetype
    From ssizetype.U:

    This variable defines ssizetype to be something like ssize_t, long or int. It is used by functions that return a count of bytes or an error condition. It must be a signed type. We will pick a type such that sizeof(SSize_t) == sizeof(Size_t).

startperl
    From startperl.U:

    This variable contains the string to put on the front of a perl script to make sure (hopefully) that it runs with perl and not some shell. Of course, that leading line must be followed by the classical perl idiom:

            eval 'exec perl -S $0 ${1+C<$@>}'
            if $running_under_some_shell;
            to guarantee perl startup should the shell execute the script. Note
    that this magic incatation is not understood by csh.

startsh
    From startsh.U:

    This variable contains the string to put on the front of a shell script to make sure (hopefully) that it runs with sh and not some other shell.

static_ext
    From Extensions.U:

    This variable holds a list of XS extension files we want to link statically into the package. It is used by Makefile.

stdchar
    From stdchar.U:

    This variable conditionally defines STDCHAR to be the type of char used in stdio.h. It has the values "unsigned char" or char.

stdio_base
    From d_stdstdio.U:

    This variable defines how, given a FILE pointer, fp, to access the _base field (or equivalent) of stdio.h's FILE structure. This will be used to define the macro FILE_base(fp).

stdio_bufsiz
    From d_stdstdio.U:

    This variable defines how, given a FILE pointer, fp, to determine the number of bytes store in the I/O buffer pointer to by the _base field (or equivalent) of stdio.h's FILE structure. This will be used to define the macro FILE_bufsiz(fp).

stdio_cnt
    From d_stdstdio.U:

    This variable defines how, given a FILE pointer, fp, to access the _cnt field (or equivalent) of stdio.h's FILE structure. This will be used to define the macro FILE_cnt(fp).

stdio_filbuf
    From d_stdstdio.U:

    This variable defines how, given a FILE pointer, fp, to tell stdio to refill it's internal buffers (?). This will be used to define the macro FILE_filbuf(fp).

stdio_ptr
    From d_stdstdio.U:

    This variable defines how, given a FILE pointer, fp, to access the _ptr field (or equivalent) of stdio.h's FILE structure. This will be used to define the macro FILE_ptr(fp).

strings
    From i_string.U:

    This variable holds the full path of the string header that will be used. Typically /usr/include/string.h or /usr/include/strings.h.

submit
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

subversion
    From patchlevel.U:

    The subversion level of this package. The value of subversion comes from the patchlevel.h file. This is unique to perl.

sysman
    From sysman.U:

    This variable holds the place where the manual is located on this system. It is not the place where the user wants to put his manual pages. Rather it is the place where Configure may look to find manual for unix commands (section 1 of the manual usually). See mansrc.

  t

tail
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

tar From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

tbl From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

tee From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the tee program. After Configure runs, the value is reset to a plain tee and is not useful.

test
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the test program. After Configure runs, the value is reset to a plain test and is not useful.

timeincl
    From i_time.U:

    This variable holds the full path of the included time header(s).

timetype
    From d_time.U:

    This variable holds the type returned by time(). It can be long, or time_t on BSD sites (in which case <sys/types.h> should be included). Anyway, the type Time_t should be used.

touch
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the touch program. After Configure runs, the value is reset to a plain touch and is not useful.

tr  From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the tr program. After Configure runs, the value is reset to a plain tr and is not useful.

trnl
    From trnl.U:

    This variable contains the value to be passed to the tr(1) command to transliterate a newline. Typical values are \012 and \n. This is needed for EBCDIC systems where newline is not necessarily \012.

troff
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

  u

uidtype
    From uidtype.U:

    This variable defines Uid_t to be something like uid_t, int, ushort, or whatever type is used to declare user ids in the kernel.

uname
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the uname program. After Configure runs, the value is reset to a plain uname and is not useful.

uniq
    From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the uniq program. After Configure runs, the value is reset to a plain uniq and is not useful.

usedl
    From dlsrc.U:

    This variable indicates if the the system supports dynamic loading of some sort. See also dlsrc and dlobj.

usemymalloc
    From mallocsrc.U:

    This variable contains y if the malloc that comes with this package is desired over the system's version of malloc. People often include special versions of malloc for effiency, but such versions are often less portable. See also mallocsrc and mallocobj. If this is y, then -lmalloc is removed from $libs.

usenm
    From usenm.U:

    This variable contains true or false depending whether the nm extraction is wanted or not.

useopcode
    From Extensions.U:

    This variable holds either true or false to indicate whether the Opcode extension should be used. The sole use for this currently is to allow an easy mechanism for users to skip the Opcode extension from the Configure command line.

useperlio
    From useperlio.U:

    This variable conditionally defines the USE_PERLIO symbol, and indicates that the PerlIO abstraction should be used throughout.

useposix
    From Extensions.U:

    This variable holds either true or false to indicate whether the POSIX extension should be used. The sole use for this currently is to allow an easy mechanism for hints files to indicate that POSIX will not compile on a particular system.

usesfio
    From d_sfio.U:

    This variable is set to true when the user agrees to use sfio. It is set to false when sfio is not available or when the user explicitely requests not to use sfio. It is here primarily so that command-line settings can override the auto-detection of d_sfio without running into a "WHOA THERE".

useshrplib
    From libperl.U:

    This variable is set to yes if the user wishes to build a shared libperl, and no otherwise.

usethreads
    From usethreads.U:

    This variable conditionally defines the USE_THREADS symbol, and indicates that Perl should be built to use threads.

usevfork
    From d_vfork.U:

    This variable is set to true when the user accepts to use vfork. It is set to false when no vfork is available or when the user explicitely requests not to use vfork.

usrinc
    From usrinc.U:

    This variable holds the path of the include files, which is usually /usr/include. It is mainly used by other Configure units.

uuname
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

  v

version
    From patchlevel.U:

    The full version number of this package. This combines baserev, patchlevel, and subversion to get the full version number, including any possible subversions. Care is taken to use the C locale in order to get something like 5.004 instead of 5,004. This is unique to perl.

vi  From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

voidflags
    From voidflags.U:

    This variable contains the eventual value of the VOIDFLAGS symbol, which indicates how much support of the void type is given by this compiler. See VOIDFLAGS for more info.

  z

zcat
    From Loc.U:

    This variable is defined but not used by Configure. The value is a plain '' and is not useful.

zip From Loc.U:

    This variable is used internally by Configure to determine the full pathname (if any) of the zip program. After Configure runs, the value is reset to a plain zip and is not useful.

NOTE
This module contains a good example of how to use tie to implement a cache and an example of how to make a tied variable readonly to those outside of it.