libexplain/fcntl.h File Reference

explain fcntl(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
int	explain_fcntl_or_die (int fildes, int command, long arg)
int	explain_fcntl_on_error (int fildes, int command, long arg) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_fcntl (int fildes, int command, long arg) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_fcntl (int errnum, int fildes, int command, long arg) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_fcntl (char *message, int message_size, int fildes, int command, long arg)
void	explain_message_errno_fcntl (char *message, int message_size, int errnum, int fildes, int command, long arg)

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Detailed Description

explain fcntl(2) errors

Definition in file fcntl.h.

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Function Documentation

const char* explain_errno_fcntl	(	int	errnum,
		int	fildes,
		int	command,
		long	arg
	)

The explain_errno_fcntl function is used to obtain an explanation of an error returned by the fcntl(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 (fcntl(fildes, command, arg) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_fcntl(err, fildes, command, arg));
     exit(EXIT_FAILURE);
 }

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

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.
fildes	The original fildes, exactly as passed to the fcntl(2) system call.
command	The original command, exactly as passed to the fcntl(2) system call.
arg	The original arg, exactly as passed to the fcntl(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.

const char* explain_fcntl	(	int	fildes,
		int	command,
		long	arg
	)

The explain_fcntl function is used to obtain an explanation of an error returned by the fcntl(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 (fcntl(fildes, command, arg) < 0)
 {
     fprintf(stderr, "%s\n", explain_fcntl(fildes, command, arg));
     exit(EXIT_FAILURE);
 }

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

Parameters:

fildes	The original fildes, exactly as passed to the fcntl(2) system call.
command	The original command, exactly as passed to the fcntl(2) system call.
arg	The original arg, exactly as passed to the fcntl(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.

int explain_fcntl_on_error	(	int	fildes,
		int	command,
		long	arg
	)

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

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

 if (explain_fcntl_on_error(fildes, command, arg) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

fildes	The fildes, exactly as to be passed to the fcntl(2) system call.
command	The command, exactly as to be passed to the fcntl(2) system call.
arg	The arg, exactly as to be passed to the fcntl(2) system call.

Returns:

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

int explain_fcntl_or_die	(	int	fildes,
		int	command,
		long	arg
	)

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

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

 explain_fcntl_or_die(fildes, command, arg);

Parameters:

fildes	The fildes, exactly as to be passed to the fcntl(2) system call.
command	The command, exactly as to be passed to the fcntl(2) system call.
arg	The arg, exactly as to be passed to the fcntl(2) system call.

Returns:

This function only returns on success. On failure, prints an explanation and exits, it does not return.

void explain_message_errno_fcntl	(	char *	message,
		int	message_size,
		int	errnum,
		int	fildes,
		int	command,
		long	arg
	)

The explain_message_errno_fcntl function is used to obtain an explanation of an error returned by the fcntl(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 (fcntl(fildes, command, arg) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_fcntl(message, sizeof(message), err, fildes,
         command, arg);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

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.
fildes	The original fildes, exactly as passed to the fcntl(2) system call.
command	The original command, exactly as passed to the fcntl(2) system call.
arg	The original arg, exactly as passed to the fcntl(2) system call.

void explain_message_fcntl	(	char *	message,
		int	message_size,
		int	fildes,
		int	command,
		long	arg
	)

The explain_message_fcntl function is used to obtain an explanation of an error returned by the fcntl(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.

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

 if (fcntl(fildes, command, arg) < 0)
 {
     char message[3000];
     explain_message_fcntl(message, sizeof(message), fildes, command, arg);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

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.
fildes	The original fildes, exactly as passed to the fcntl(2) system call.
command	The original command, exactly as passed to the fcntl(2) system call.
arg	The original arg, exactly as passed to the fcntl(2) system call.