explain_linkat(3)

NAME
explain_linkat - explain linkat(2) errors

SYNOPSIS
#include <libexplain/linkat.h>

const char *explain_linkat(int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);
const char *explain_errno_linkat(int errnum, int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);
void explain_message_linkat(char *message, int message_size, int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);
void explain_message_errno_linkat(char *message, int message_size, int errnum, int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);

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

  explain_linkat
const char *explain_linkat(int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);

The explain_linkat function is used to obtain an explanation of an error returned by the linkat(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.

old_fildes
    The original old_fildes, exactly as passed to the linkat(2) system call.

old_path
    The original old_path, exactly as passed to the linkat(2) system call.

new_fildes
    The original new_fildes, exactly as passed to the linkat(2) system call.

new_path
    The original new_path, exactly as passed to the linkat(2) system call.

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

Example: This function is intended to be used in a fashion similar to the following example:
    if (linkat(old_fildes, old_path, new_fildes, new_path, flags) < 0)
    {
    fprintf(stderr, "%s\n", explain_linkat(old_fildes, old_path, new_fildes, new_path, flags));
        exit(EXIT_FAILURE);
    }

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

  explain_errno_linkat
const char *explain_errno_linkat(int errnum, int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);

The explain_errno_linkat function is used to obtain an explanation of an error returned by the linkat(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.

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.

old_fildes
    The original old_fildes, exactly as passed to the linkat(2) system call.

old_path
    The original old_path, exactly as passed to the linkat(2) system call.

new_fildes
    The original new_fildes, exactly as passed to the linkat(2) system call.

new_path
    The original new_path, exactly as passed to the linkat(2) system call.

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

Example: This function is intended to be used in a fashion similar to the following example:
    if (linkat(old_fildes, old_path, new_fildes, new_path, flags) < 0)
    {
        int err = errno;
    fprintf(stderr, "%s\n", explain_errno_linkat(err, old_fildes, old_path, new_fildes, new_path, flags));
        exit(EXIT_FAILURE);
    }

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

  explain_message_linkat
void explain_message_linkat(char *message, int message_size, int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);

The explain_message_linkat function is used to obtain an explanation of an error returned by the linkat(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.

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.

old_fildes
    The original old_fildes, exactly as passed to the linkat(2) system call.

old_path
    The original old_path, exactly as passed to the linkat(2) system call.

new_fildes
    The original new_fildes, exactly as passed to the linkat(2) system call.

new_path
    The original new_path, exactly as passed to the linkat(2) system call.

flags
    The original flags, exactly as passed to the linkat(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (linkat(old_fildes, old_path, new_fildes, new_path, flags) < 0)
    {
        char message[3000];
    explain_message_linkat(message, sizeof(message), old_fildes, old_path, new_fildes, new_path, flags);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

  explain_message_errno_linkat
void explain_message_errno_linkat(char *message, int message_size, int errnum, int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags);

The explain_message_errno_linkat function is used to obtain an explanation of an error returned by the linkat(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.

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.

old_fildes
    The original old_fildes, exactly as passed to the linkat(2) system call.

old_path
    The original old_path, exactly as passed to the linkat(2) system call.

new_fildes
    The original new_fildes, exactly as passed to the linkat(2) system call.

new_path
    The original new_path, exactly as passed to the linkat(2) system call.

flags
    The original flags, exactly as passed to the linkat(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (linkat(old_fildes, old_path, new_fildes, new_path, flags) < 0)
    {
        int err = errno;
        char message[3000];
    explain_message_errno_linkat(message, sizeof(message), err, old_fildes, old_path, new_fildes, new_path, flags);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

SEE ALSO

linkat(2)
    create a file link relative to directory file descriptors

explain_linkat_or_die(3)
    create a file link relative to directory file descriptors and report errors

COPYRIGHT
libexplain version 1.4
Copyright (C) 2013 Peter Miller