libexplain/ftruncate.h File Reference

explain ftruncate(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_ftruncate_or_die (int fildes, off_t length)
int	explain_ftruncate_on_error (int fildes, off_t length)
const char *	explain_ftruncate (int fildes, off_t length) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_ftruncate (int errnum, int fildes, off_t length) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_ftruncate (char *message, int message_size, int fildes, off_t length)
void	explain_message_errno_ftruncate (char *message, int message_size, int errnum, int fildes, off_t length)

---

Detailed Description

explain ftruncate(2) errors

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

Definition in file ftruncate.h.

---

Function Documentation

const char* explain_errno_ftruncate	(	int	errnum,
		int	fildes,
		off_t	length
	)

The explain_errno_ftruncate function is used to obtain an explanation of an error returned by the ftruncate(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.
fildes	The original fildes, exactly as passed to the ftruncate(2) system call.
length	The original length, exactly as passed to the ftruncate(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 (ftruncate(fildes, length) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_ftruncate(err, fildes, length));
     exit(EXIT_FAILURE);
 }

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

const char* explain_ftruncate	(	int	fildes,
		off_t	length
	)

The explain_ftruncate function is used to obtain an explanation of an error returned by the ftruncate(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:

fildes	The original fildes, exactly as passed to the ftruncate(2) system call.
length	The original length, exactly as passed to the ftruncate(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 (ftruncate(fildes, length) < 0)
 {
     fprintf(stderr, "%s\n", explain_ftruncate(fildes, length));
     exit(EXIT_FAILURE);
 }

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

int explain_ftruncate_on_error	(	int	fildes,
		off_t	length
	)

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

Parameters:

fildes	The fildes, exactly as to be passed to the ftruncate(2) system call.
length	The length, exactly as to be passed to the ftruncate(2) system call.

Returns:

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

Example:

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

 if (explain_ftruncate_on_error(fildes, length) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_ftruncate_or_die	(	int	fildes,
		off_t	length
	)

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

Parameters:

fildes	The fildes, exactly as to be passed to the ftruncate(2) system call.
length	The length, exactly as to be passed to the ftruncate(2) system call.

Returns:

This function only returns on success, see ftruncate(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_ftruncate_or_die(fildes, length);

void explain_message_errno_ftruncate	(	char *	message,
		int	message_size,
		int	errnum,
		int	fildes,
		off_t	length
	)

The explain_message_errno_ftruncate function is used to obtain an explanation of an error returned by the ftruncate(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.
fildes	The original fildes, exactly as passed to the ftruncate(2) system call.
length	The original length, exactly as passed to the ftruncate(2) system call.

Example:

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

 if (ftruncate(fildes, length) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_ftruncate(message, sizeof(message), err, fildes,
         length);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

void explain_message_ftruncate	(	char *	message,
		int	message_size,
		int	fildes,
		off_t	length
	)

The explain_message_ftruncate function is used to obtain an explanation of an error returned by the ftruncate(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.
fildes	The original fildes, exactly as passed to the ftruncate(2) system call.
length	The original length, exactly as passed to the ftruncate(2) system call.

Example:

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

 if (ftruncate(fildes, length) < 0)
 {
     char message[3000];
     explain_message_ftruncate(message, sizeof(message), fildes, length);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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