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explain_dup2

explain_dup2

Section: C Library Functions (3)
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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 0.37
Copyright (C) 2008 Peter Miller


 

Index

NAME
SYNOPSIS
DESCRIPTION
explain_dup2
explain_errno_dup2
explain_message_dup2
explain_message_errno_dup2
SEE ALSO
COPYRIGHT

This document was created by man2html, using the manual pages.
Time: 21:45:47 GMT, April 16, 2011