explain_fdopen(3)

NAME
explain_fdopen - explain fdopen(3) errors

SYNOPSIS
#include <libexplain/fdopen.h>

const char *explain_fdopen(int fildes, const char *flags);
const char *explain_errno_fdopen(int errnum, int fildes, const char *flags);
void explain_message_fdopen(char *message, int message_size, int fildes, const char *flags);
void explain_message_errno_fdopen(char *message, int message_size, int errnum, int fildes, const char *flags);

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

  explain_fdopen
const char *explain_fdopen(int fildes, const char *flags);

The explain_fdopen function is used to obtain an explanation of an error returned by the fdopen(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.

This function is intended to be used in a fashion similar to the following example:
    FILE *fp = fdopen(fildes, flags);
    if (!fp)
    {
        fprintf(stderr, "%s\n", explain_fdopen(fildes, flags));
        exit(EXIT_FAILURE);
    }

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

fildes
    The original fildes, exactly as passed to the fdopen(3) system call.

flags
    The original flags, exactly as passed to the fdopen(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.

  explain_errno_fdopen
const char *explain_errno_fdopen(int errnum, int fildes, const char *flags);

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

This function is intended to be used in a fashion similar to the following example:
    FILE *fp = fdopen(fildes, flags);
    if (!fp)
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_fdopen(err, fildes, flags));
        exit(EXIT_FAILURE);
    }

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

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.

fildes
    The original fildes, exactly as passed to the fdopen(3) system call.

flags
    The original flags, exactly as passed to the fdopen(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.

  explain_message_fdopen
void explain_message_fdopen(char *message, int message_size, int fildes, const char *flags);

The explain_message_fdopen function may be used to obtain an explanation of an error returned by the fdopen(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.

This function is intended to be used in a fashion similar to the following example:
    FILE *fp = fdopen(fildes, flags);
    if (!fp)
    {
        char message[3000];
        explain_message_fdopen(message, sizeof(message), fildes, flags);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

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.

fildes
    The original fildes, exactly as passed to the fdopen(3) system call.

flags
    The original flags, exactly as passed to the fdopen(3) system call.

  explain_message_errno_fdopen
void explain_message_errno_fdopen(char *message, int message_size, int errnum, int fildes, const char *flags);

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

This function is intended to be used in a fashion similar to the following example:
    FILE *fp = fdopen(fildes, flags);
    if (!fp)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_fdopen(message, sizeof(message),
            err, fildes, flags);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

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.

fildes
    The original fildes, exactly as passed to the fdopen(3) system call.

flags
    The original flags, exactly as passed to the fdopen(3) system call.

SEE ALSO

fdopen(3)
    stream open functions

explain_fdopen_or_die(3)
    stream open functions and report errors

COPYRIGHT
libexplain version 0.46
Copyright (C) 2008 Peter Miller