explain_link(3)

NAME
explain_link - explain link(2) errors

SYNOPSIS
#include <libexplain/link.h>

const char *explain_link(const char *oldpath, const char *newpath);
const char *explain_errno_link(int errnum, const char *oldpath, const char *newpath);
void explain_message_link(char *message, int message_size, const char *oldpath, const char *newpath);
void explain_message_errno_link(char *message, int message_size, int errnum, const char *oldpath, const char *newpath);

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

  explain_link
const char *explain_link(const char *oldpath, const char *newpath);

The explain_link function is used to obtain an explanation of an error returned by the link(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 (link(oldpath, newpath) < 0)
    {
        fprintf(stderr, "%s\n", explain_link(oldpath, newpath));
        exit(EXIT_FAILURE);
    }

oldpath
    The original oldpath, exactly as passed to the link(2) system call.

newpath
    The original newpath, exactly as passed to the link(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_link
const char *explain_errno_link(int errnum, const char *oldpath, const char *newpath);

The explain_errno_link function is used to obtain an explanation of an error returned by the link(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 (link(oldpath, newpath) < 0)
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_link(err, oldpath, newpath));
        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.

oldpath
    The original oldpath, exactly as passed to the link(2) system call.

newpath
    The original newpath, exactly as passed to the link(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_link
void explain_message_link(char *message, int message_size, const char *oldpath, const char *newpath);

The explain_message_link function may be used to obtain an explanation of an error returned by the link(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 (link(oldpath, newpath) < 0)
    {
        char message[3000];
        explain_message_link(message, sizeof(message), oldpath, newpath);
        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.

oldpath
    The original oldpath, exactly as passed to the link(2) system call.

newpath
    The original newpath, exactly as passed to the link(2) system call.

  explain_message_errno_link
void explain_message_errno_link(char *message, int message_size, int errnum, const char *oldpath, const char *newpath);

The explain_message_errno_link function may be used to obtain an explanation of an error returned by the link(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 (link(oldpath, newpath) < 0)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_link(message, sizeof(message), err,
            oldpath, newpath);
        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.

oldpath
    The original oldpath, exactly as passed to the link(2) system call.

newpath
    The original newpath, exactly as passed to the link(2) system call.

SEE ALSO

link(2)
    make a new name for a file

explain_link_or_die(3)
    make a new name for a file and report errors

COPYRIGHT
libexplain version
Copyright (C) 2008 Peter Miller