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 0.19
Copyright (C) 2008 Peter Miller
explain_chown(3)