explain_setenv(3)

NAME
explain_setenv - explain setenv(3) errors

SYNOPSIS
#include <libexplain/setenv.h>

const char *explain_setenv(const char *name, const char *value, int overwrite);
const char *explain_errno_setenv(int errnum, const char *name, const char *value, int overwrite);
void explain_message_setenv(char *message, int message_size, const char *name, const char *value, int overwrite);
void explain_message_errno_setenv(char *message, int message_size, int errnum, const char *name, const char *value, int overwrite);

DESCRIPTION
These functions may be used to obtain explanations for errors returned by the setenv(3) system call.

  explain_setenv
const char *explain_setenv(const char *name, const char *value, int overwrite);

The explain_setenv function is used to obtain an explanation of an error returned by the setenv(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

name
    The original name, exactly as passed to the setenv(3) system call.

value
    The original value, exactly as passed to the setenv(3) system call.

overwrite
    The original overwrite, exactly as passed to the setenv(3) system call.

Returns:
    The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setenv(name, value, overwrite) < 0)
    {
    fprintf(stderr, "%s\n", explain_setenv(name, value, overwrite));
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_setenv_or_die(3) function.

  explain_errno_setenv
const char *explain_errno_setenv(int errnum, const char *name, const char *value, int overwrite);

The explain_errno_setenv function is used to obtain an explanation of an error returned by the setenv(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

errnum
    The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.

name
    The original name, exactly as passed to the setenv(3) system call.

value
    The original value, exactly as passed to the setenv(3) system call.

overwrite
    The original overwrite, exactly as passed to the setenv(3) system call.

Returns:
    The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setenv(name, value, overwrite) < 0)
    {
        int err = errno;
    fprintf(stderr, "%s\n", explain_errno_setenv(err, name, value, overwrite));
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_setenv_or_die(3) function.

  explain_message_setenv
void explain_message_setenv(char *message, int message_size, const char *name, const char *value, int overwrite);

The explain_message_setenv function is used to obtain an explanation of an error returned by the setenv(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

message
    The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

message_size
    The size in bytes of the location in which to store the returned message.

name
    The original name, exactly as passed to the setenv(3) system call.

value
    The original value, exactly as passed to the setenv(3) system call.

overwrite
    The original overwrite, exactly as passed to the setenv(3) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setenv(name, value, overwrite) < 0)
    {
        char message[3000];
    explain_message_setenv(message, sizeof(message), name, value, overwrite);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_setenv_or_die(3) function.

  explain_message_errno_setenv
void explain_message_errno_setenv(char *message, int message_size, int errnum, const char *name, const char *value, int overwrite);

The explain_message_errno_setenv function is used to obtain an explanation of an error returned by the setenv(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

message
    The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

message_size
    The size in bytes of the location in which to store the returned message.

errnum
    The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.

name
    The original name, exactly as passed to the setenv(3) system call.

value
    The original value, exactly as passed to the setenv(3) system call.

overwrite
    The original overwrite, exactly as passed to the setenv(3) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setenv(name, value, overwrite) < 0)
    {
        int err = errno;
        char message[3000];
    explain_message_errno_setenv(message, sizeof(message), err, name, value, overwrite);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_setenv_or_die(3) function.

SEE ALSO

setenv(3)
    change or add an environment variable

explain_setenv_or_die(3)
    change or add an environment variable and report errors

COPYRIGHT
libexplain version 1.1
Copyright (C) 2010 Peter Miller