Provided by: libexplain-dev_1.4.D001-7_amd64 
NAME
explain_dup2 - explain dup2(2) errors
SYNOPSIS
#include <libexplain/dup2.h>
const char *explain_dup2(int oldfd, int newfd);
const char *explain_errno_dup2(int errnum, int oldfd, int newfd);
void explain_message_dup2(char *message, int message_size, int oldfd, int newfd);
void explain_message_errno_dup2(char *message, int message_size, int errnum, int oldfd, int newfd);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the dup2(2) system call.
explain_dup2
const char *explain_dup2(int oldfd, int newfd);
The explain_dup2 function is used to obtain an explanation of an error returned by the dup2(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 (dup2(oldfd, newfd) < 0)
{
fprintf(stderr, "%s\n", explain_dup2(oldfd, newfd));
exit(EXIT_FAILURE);
}
oldfd The original oldfd, exactly as passed to the dup2(2) system call.
newfd The original newfd, exactly as passed to the dup2(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_dup2
const char *explain_errno_dup2(int errnum, int oldfd, int newfd);
The explain_errno_dup2 function is used to obtain an explanation of an error returned by the dup2(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 (dup2(oldfd, newfd) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_dup2(err, oldfd, newfd));
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.
oldfd The original oldfd, exactly as passed to the dup2(2) system call.
newfd The original newfd, exactly as passed to the dup2(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_dup2
void explain_message_dup2(char *message, int message_size, int oldfd, int newfd);
The explain_message_dup2 function may be used to obtain an explanation of an error returned by the
dup2(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 (dup2(oldfd, newfd) < 0)
{
char message[3000];
explain_message_dup2(message, sizeof(message), oldfd, newfd);
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.
oldfd The original oldfd, exactly as passed to the dup2(2) system call.
newfd The original newfd, exactly as passed to the dup2(2) system call.
explain_message_errno_dup2
void explain_message_errno_dup2(char *message, int message_size, int errnum, int oldfd, int newfd);
The explain_message_errno_dup2 function may be used to obtain an explanation of an error returned by the
dup2(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 (dup2(oldfd, newfd) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_dup2(message, sizeof(message), err, oldfd, newfd);
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.
oldfd The original oldfd, exactly as passed to the dup2(2) system call.
newfd The original newfd, exactly as passed to the dup2(2) system call.
SEE ALSO
dup2(2) duplicate a file descriptor
explain_dup2_or_die(3)
duplicate a file descriptor and report errors
COPYRIGHT
libexplain version 1.4
Copyright (C) 2008 Peter Miller
explain_dup2(3)