libexplain/fchownat.h File Reference

explain fchownat(2) errors More...

#include <libexplain/gcc_attributes.h>
#include <libexplain/large_file_support.h>
#include <unistd.h>

Go to the source code of this file.

Functions
void	explain_fchownat_or_die (int dirfd, const char *pathname, int owner, int group, int flags)
int	explain_fchownat_on_error (int dirfd, const char *pathname, int owner, int group, int flags)
const char *	explain_fchownat (int dirfd, const char *pathname, int owner, int group, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_fchownat (int errnum, int dirfd, const char *pathname, int owner, int group, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_fchownat (char *message, int message_size, int dirfd, const char *pathname, int owner, int group, int flags)
void	explain_message_errno_fchownat (char *message, int message_size, int errnum, int dirfd, const char *pathname, int owner, int group, int flags)

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Detailed Description

explain fchownat(2) errors

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

Definition in file fchownat.h.

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Function Documentation

const char* explain_errno_fchownat	(	int	errnum,
		int	dirfd,
		const char *	pathname,
		int	owner,
		int	group,
		int	flags
	)

The explain_errno_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.

Parameters:

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.
dirfd	The original dirfd, exactly as passed to the fchownat(2) system call.
pathname	The original pathname, exactly as passed to the fchownat(2) system call.
owner	The original owner, exactly as passed to the fchownat(2) system call.
group	The original group, exactly as passed to the fchownat(2) system call.
flags	The original flags, exactly as passed to the fchownat(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 (fchownat(dirfd, pathname, owner, group, flags) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_fchownat(err, dirfd, pathname,
         owner, group, flags));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_fchownat_or_die function.

const char* explain_fchownat	(	int	dirfd,
		const char *	pathname,
		int	owner,
		int	group,
		int	flags
	)

The explain_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.

Parameters:

dirfd	The original dirfd, exactly as passed to the fchownat(2) system call.
pathname	The original pathname, exactly as passed to the fchownat(2) system call.
owner	The original owner, exactly as passed to the fchownat(2) system call.
group	The original group, exactly as passed to the fchownat(2) system call.
flags	The original flags, exactly as passed to the fchownat(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 (fchownat(dirfd, pathname, owner, group, flags) < 0)
 {
     explain_output_error_and_die("%s\n", explain_fchownat(dirfd, pathname,
         owner, group, flags));
 }

The above code example is available pre\-packaged as the explain_fchownat_or_die function.

int explain_fchownat_on_error	(	int	dirfd,
		const char *	pathname,
		int	owner,
		int	group,
		int	flags
	)

The explain_fchownat_on_error function is used to call the fchownat(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_fchownat(3) function.

Parameters:

dirfd	The dirfd, exactly as to be passed to the fchownat(2) system call.
pathname	The pathname, exactly as to be passed to the fchownat(2) system call.
owner	The owner, exactly as to be passed to the fchownat(2) system call.
group	The group, exactly as to be passed to the fchownat(2) system call.
flags	The flags, exactly as to be passed to the fchownat(2) system call.

Returns:

The value returned by the wrapped fchownat(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (explain_fchownat_on_error(dirfd, pathname, owner, group, flags) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_fchownat_or_die	(	int	dirfd,
		const char *	pathname,
		int	owner,
		int	group,
		int	flags
	)

The explain_fchownat_or_die function is used to call the fchownat(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_fchownat(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

Parameters:

dirfd	The dirfd, exactly as to be passed to the fchownat(2) system call.
pathname	The pathname, exactly as to be passed to the fchownat(2) system call.
owner	The owner, exactly as to be passed to the fchownat(2) system call.
group	The group, exactly as to be passed to the fchownat(2) system call.
flags	The flags, exactly as to be passed to the fchownat(2) system call.

Returns:

This function only returns on success, see fchownat(2) for more information. On failure, prints an explanation and exits, it does not return.

Example:

This function is intended to be used in a fashion similar to the following example:

 explain_fchownat_or_die(dirfd, pathname, owner, group, flags);

void explain_message_errno_fchownat	(	char *	message,
		int	message_size,
		int	errnum,
		int	dirfd,
		const char *	pathname,
		int	owner,
		int	group,
		int	flags
	)

The explain_message_errno_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.

Parameters:

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.
dirfd	The original dirfd, exactly as passed to the fchownat(2) system call.
pathname	The original pathname, exactly as passed to the fchownat(2) system call.
owner	The original owner, exactly as passed to the fchownat(2) system call.
group	The original group, exactly as passed to the fchownat(2) system call.
flags	The original flags, exactly as passed to the fchownat(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (fchownat(dirfd, pathname, owner, group, flags) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_fchownat(message, sizeof(message), err, dirfd,
         pathname, owner, group, flags);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_fchownat_or_die function.

void explain_message_fchownat	(	char *	message,
		int	message_size,
		int	dirfd,
		const char *	pathname,
		int	owner,
		int	group,
		int	flags
	)

The explain_message_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.

The errno global variable will be used to obtain the error value to be decoded.

Parameters:

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.
dirfd	The original dirfd, exactly as passed to the fchownat(2) system call.
pathname	The original pathname, exactly as passed to the fchownat(2) system call.
owner	The original owner, exactly as passed to the fchownat(2) system call.
group	The original group, exactly as passed to the fchownat(2) system call.
flags	The original flags, exactly as passed to the fchownat(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (fchownat(dirfd, pathname, owner, group, flags) < 0)
 {
     char message[3000];
     explain_message_fchownat(message, sizeof(message), dirfd, pathname,
         owner, group, flags);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_fchownat_or_die function.