explain_dup(3)

NAME
explain_dup - explain dup(2) errors

SYNOPSIS
#include <libexplain/dup.h>

const char *explain_dup(int fildes);
const char *explain_errno_dup(int errnum, int fildes);
void explain_message_dup(char *message, int message_size, int fildes);
void explain_message_errno_dup(char *message, int message_size, int errnum, int fildes);

DESCRIPTION
These functions may be used to obtain explanations for errors returned by the dup(2) system call.

  explain_dup
const char *explain_dup(int fildes);

The explain_dup function is used to obtain an explanation of an error returned by the dup(2) 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:
    if (dup(fildes) < 0)
    {
        fprintf(stderr, "%s\n", explain_dup(fildes));
        exit(EXIT_FAILURE);
    }

fildes
    The original fildes, exactly as passed to the dup(2) 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_dup
const char *explain_errno_dup(int errnum, int fildes);

The explain_errno_dup function is used to obtain an explanation of an error returned by the dup(2) 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:
    if (dup(fildes) < 0)
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_dup(err, fildes));
        exit(EXIT_FAILURE);
    }

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 dup(2) 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_dup
void explain_message_dup(char *message, int message_size, int fildes);

The explain_message_dup function may be used to obtain an explanation of an error returned by the dup(2) 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:
    if (dup(fildes) < 0)
    {
        char message[3000];
        explain_message_dup(message, sizeof(message), fildes);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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 dup(2) system call.

  explain_message_errno_dup
void explain_message_errno_dup(char *message, int message_size, int errnum, int fildes);

The explain_message_errno_dup function may be used to obtain an explanation of an error returned by the dup(2) 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:
    if (dup(fildes) < 0)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_dup(message, sizeof(message), err, fildes);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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 dup(2) system call.

SEE ALSO

dup(2)
    duplicate a file descriptor

explain_dup_or_die(3)
    duplicate a file descriptor and report errors

COPYRIGHT
libexplain version
Copyright (C) 2008 Peter Miller