libexplain/setpriority.h File Reference

explain setpriority(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_setpriority_or_die (int which, int who, int prio)
int	explain_setpriority_on_error (int which, int who, int prio)
const char *	explain_setpriority (int which, int who, int prio) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_setpriority (int errnum, int which, int who, int prio) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_setpriority (char *message, int message_size, int which, int who, int prio)
void	explain_message_errno_setpriority (char *message, int message_size, int errnum, int which, int who, int prio)

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Detailed Description

explain setpriority(2) errors

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

Definition in file setpriority.h.

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Function Documentation

const char* explain_errno_setpriority	(	int	errnum,
		int	which,
		int	who,
		int	prio
	)

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

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

void explain_message_errno_setpriority	(	char *	message,
		int	message_size,
		int	errnum,
		int	which,
		int	who,
		int	prio
	)

The explain_message_errno_setpriority function is used to obtain an explanation of an error returned by the setpriority(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.
which	The original which, exactly as passed to the setpriority(2) system call.
who	The original who, exactly as passed to the setpriority(2) system call.
prio	The original prio, exactly as passed to the setpriority(2) system call.

Example:

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

 if (setpriority(which, who, prio) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_setpriority(message, sizeof(message), err, which,
         who, prio);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

void explain_message_setpriority	(	char *	message,
		int	message_size,
		int	which,
		int	who,
		int	prio
	)

The explain_message_setpriority function is used to obtain an explanation of an error returned by the setpriority(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.
which	The original which, exactly as passed to the setpriority(2) system call.
who	The original who, exactly as passed to the setpriority(2) system call.
prio	The original prio, exactly as passed to the setpriority(2) system call.

Example:

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

 if (setpriority(which, who, prio) < 0)
 {
     char message[3000];
     explain_message_setpriority(message, sizeof(message), which, who, prio);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

const char* explain_setpriority	(	int	which,
		int	who,
		int	prio
	)

The explain_setpriority function is used to obtain an explanation of an error returned by the setpriority(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:

which	The original which, exactly as passed to the setpriority(2) system call.
who	The original who, exactly as passed to the setpriority(2) system call.
prio	The original prio, exactly as passed to the setpriority(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 (setpriority(which, who, prio) < 0)
 {
     explain_output_error_and_die("%s\n", explain_setpriority(which, who,
         prio));
 }

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

int explain_setpriority_on_error	(	int	which,
		int	who,
		int	prio
	)

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

Parameters:

which	The which, exactly as to be passed to the setpriority(2) system call.
who	The who, exactly as to be passed to the setpriority(2) system call.
prio	The prio, exactly as to be passed to the setpriority(2) system call.

Returns:

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

Example:

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

 if (explain_setpriority_on_error(which, who, prio) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_setpriority_or_die	(	int	which,
		int	who,
		int	prio
	)

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

Parameters:

which	The which, exactly as to be passed to the setpriority(2) system call.
who	The who, exactly as to be passed to the setpriority(2) system call.
prio	The prio, exactly as to be passed to the setpriority(2) system call.

Returns:

This function only returns on success, see setpriority(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_setpriority_or_die(which, who, prio);