libexplain/linkat.h File Reference

explain linkat(2) errors More...

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

Go to the source code of this file.

Functions
void	explain_linkat_or_die (int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags)
int	explain_linkat_on_error (int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags)
const char *	explain_linkat (int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_linkat (int errnum, int old_fildes, const char *old_path, int new_fildes, const char *new_path, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
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)

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Detailed Description

explain linkat(2) errors

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

Definition in file linkat.h.

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Function Documentation

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(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.
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;
     explain_output_error_and_die("%s", explain_errno_linkat(err, old_fildes,
         old_path, new_fildes, new_path, flags));
 }

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

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.

Parameters:

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)
 {
     explain_output_error_and_die("%s\n", explain_linkat(old_fildes,
         old_path, new_fildes, new_path, flags));
 }

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

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

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

Parameters:

old_fildes	The old_fildes, exactly as to be passed to the linkat(2) system call.
old_path	The old_path, exactly as to be passed to the linkat(2) system call.
new_fildes	The new_fildes, exactly as to be passed to the linkat(2) system call.
new_path	The new_path, exactly as to be passed to the linkat(2) system call.
flags	The flags, exactly as to be passed to the linkat(2) system call.

Returns:

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

Example:

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

 if (explain_linkat_on_error(old_fildes, old_path, new_fildes, new_path,
     flags) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_linkat_or_die	(	int	old_fildes,
		const char *	old_path,
		int	new_fildes,
		const char *	new_path,
		int	flags
	)

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

Parameters:

old_fildes	The old_fildes, exactly as to be passed to the linkat(2) system call.
old_path	The old_path, exactly as to be passed to the linkat(2) system call.
new_fildes	The new_fildes, exactly as to be passed to the linkat(2) system call.
new_path	The new_path, exactly as to be passed to the linkat(2) system call.
flags	The flags, exactly as to be passed to the linkat(2) system call.

Returns:

This function only returns on success, see linkat(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_linkat_or_die(old_fildes, old_path, new_fildes, new_path, 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
	)

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(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.
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);
     explain_output_error_and_die("%s", message);
 }

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

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(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.
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);
     explain_output_error_and_die("%s", message);  * }

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