explain_chown(3)

NAME
explain_chown - explain chown(2) errors

SYNOPSIS
#include <libexplain/chown.h>

const char *explain_chown(const char *pathname, int owner, int group);
const char *explain_errno_chown(int errnum, const char *pathname, int owner, int group);
void explain_message_chown(char *message, int message_size, const char *pathname, int owner, int group);
void explain_message_errno_chown(char *message, int message_size, int errnum, const char *pathname, int owner, int group);

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

  explain_chown
const char *explain_chown(const char *pathname, int owner, int group);

The explain_chown function is used to obtain an explanation of an error returned by the chown(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 (chown(pathname, owner, group) < 0)
    {
        fprintf(stderr, "%s\n", explain_chown(pathname, owner, group));
        exit(EXIT_FAILURE);
    }

pathname
    The original pathname, exactly as passed to the chown(2) system call.

owner
    The original owner, exactly as passed to the chown(2) system call.

group
    The original group, exactly as passed to the chown(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_chown
const char *explain_errno_chown(int errnum, const char *pathname, int owner, int group);

The explain_errno_chown function is used to obtain an explanation of an error returned by the chown(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 (chown(pathname, owner, group) < 0)
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_chown(err, pathname, owner,
            group));
        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.

pathname
    The original pathname, exactly as passed to the chown(2) system call.

owner
    The original owner, exactly as passed to the chown(2) system call.

group
    The original group, exactly as passed to the chown(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_chown
void explain_message_chown(char *message, int message_size, const char *pathname, int owner, int group);

The explain_message_chown function may be used to obtain an explanation of an error returned by the chown(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 (chown(pathname, owner, group) < 0)
    {
        char message[3000];
        explain_message_chown(message, sizeof(message), pathname, owner, group);
        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.

pathname
    The original pathname, exactly as passed to the chown(2) system call.

owner
    The original owner, exactly as passed to the chown(2) system call.

group
    The original group, exactly as passed to the chown(2) system call.

  explain_message_errno_chown
void explain_message_errno_chown(char *message, int message_size, int errnum, const char *pathname, int owner, int group);

The explain_message_errno_chown function may be used to obtain an explanation of an error returned by the chown(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 (chown(pathname, owner, group) < 0)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_chown(message, sizeof(message), err,
            pathname, owner, group);
        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.

pathname
    The original pathname, exactly as passed to the chown(2) system call.

owner
    The original owner, exactly as passed to the chown(2) system call.

group
    The original group, exactly as passed to the chown(2) system call.

SEE ALSO

chown(2)
    change ownership of a file

explain_chown_or_die(3)
    change ownership of a file and report errors

COPYRIGHT
libexplain version 0.46
Copyright (C) 2008 Peter Miller