libexplain/shmctl.h File Reference

explain shmctl(2) errors More...

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

Go to the source code of this file.

Functions
int	explain_shmctl_or_die (int shmid, int command, struct shmid_ds *data)
int	explain_shmctl_on_error (int shmid, int command, struct shmid_ds *data)
const char *	explain_shmctl (int shmid, int command, struct shmid_ds *data) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_shmctl (int errnum, int shmid, int command, struct shmid_ds *data) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_shmctl (char *message, int message_size, int shmid, int command, struct shmid_ds *data)
void	explain_message_errno_shmctl (char *message, int message_size, int errnum, int shmid, int command, struct shmid_ds *data)

---

Detailed Description

explain shmctl(2) errors

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

Definition in file shmctl.h.

---

Function Documentation

const char* explain_errno_shmctl	(	int	errnum,
		int	shmid,
		int	command,
		struct shmid_ds *	data
	)

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

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

void explain_message_errno_shmctl	(	char *	message,
		int	message_size,
		int	errnum,
		int	shmid,
		int	command,
		struct shmid_ds *	data
	)

The explain_message_errno_shmctl function is used to obtain an explanation of an error returned by the shmctl(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.
shmid	The original shmid, exactly as passed to the shmctl(2) system call.
command	The original command, exactly as passed to the shmctl(2) system call.
data	The original data, exactly as passed to the shmctl(2) system call.

Example:

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

 if (shmctl(shmid, command, data) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_shmctl(message, sizeof(message), err, shmid,
         command, data);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

void explain_message_shmctl	(	char *	message,
		int	message_size,
		int	shmid,
		int	command,
		struct shmid_ds *	data
	)

The explain_message_shmctl function is used to obtain an explanation of an error returned by the shmctl(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.
shmid	The original shmid, exactly as passed to the shmctl(2) system call.
command	The original command, exactly as passed to the shmctl(2) system call.
data	The original data, exactly as passed to the shmctl(2) system call.

Example:

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

 if (shmctl(shmid, command, data) < 0)
 {
     char message[3000];
     explain_message_shmctl(message, sizeof(message), shmid, command, data);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

const char* explain_shmctl	(	int	shmid,
		int	command,
		struct shmid_ds *	data
	)

The explain_shmctl function is used to obtain an explanation of an error returned by the shmctl(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:

shmid	The original shmid, exactly as passed to the shmctl(2) system call.
command	The original command, exactly as passed to the shmctl(2) system call.
data	The original data, exactly as passed to the shmctl(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 (shmctl(shmid, command, data) < 0)
 {
     fprintf(stderr, "%s\n", explain_shmctl(shmid, command, data));
     exit(EXIT_FAILURE);
 }

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

int explain_shmctl_on_error	(	int	shmid,
		int	command,
		struct shmid_ds *	data
	)

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

Parameters:

shmid	The shmid, exactly as to be passed to the shmctl(2) system call.
command	The command, exactly as to be passed to the shmctl(2) system call.
data	The data, exactly as to be passed to the shmctl(2) system call.

Returns:

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

Example:

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

 if (explain_shmctl_on_error(shmid, command, data) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

int explain_shmctl_or_die	(	int	shmid,
		int	command,
		struct shmid_ds *	data
	)

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

Parameters:

shmid	The shmid, exactly as to be passed to the shmctl(2) system call.
command	The command, exactly as to be passed to the shmctl(2) system call.
data	The data, exactly as to be passed to the shmctl(2) system call.

Returns:

This function only returns on success, see shmctl(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_shmctl_or_die(shmid, command, data);