libexplain/getrusage.h File Reference

explain getrusage(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_getrusage_or_die (int who, struct rusage *usage)
int	explain_getrusage_on_error (int who, struct rusage *usage)
const char *	explain_getrusage (int who, struct rusage *usage) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_getrusage (int errnum, int who, struct rusage *usage) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_getrusage (char *message, int message_size, int who, struct rusage *usage)
void	explain_message_errno_getrusage (char *message, int message_size, int errnum, int who, struct rusage *usage)

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Detailed Description

explain getrusage(2) errors

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

Definition in file getrusage.h.

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Function Documentation

const char* explain_errno_getrusage	(	int	errnum,
		int	who,
		struct rusage *	usage
	)

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

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

const char* explain_getrusage	(	int	who,
		struct rusage *	usage
	)

The explain_getrusage function is used to obtain an explanation of an error returned by the getrusage(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:

who	The original who, exactly as passed to the getrusage(2) system call.
usage	The original usage, exactly as passed to the getrusage(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 (getrusage(who, usage) < 0)
 {
     fprintf(stderr, "%s\n", explain_getrusage(who, usage));
     exit(EXIT_FAILURE);
 }

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

int explain_getrusage_on_error	(	int	who,
		struct rusage *	usage
	)

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

Parameters:

who	The who, exactly as to be passed to the getrusage(2) system call.
usage	The usage, exactly as to be passed to the getrusage(2) system call.

Returns:

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

Example:

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

 if (explain_getrusage_on_error(who, usage) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_getrusage_or_die	(	int	who,
		struct rusage *	usage
	)

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

Parameters:

who	The who, exactly as to be passed to the getrusage(2) system call.
usage	The usage, exactly as to be passed to the getrusage(2) system call.

Returns:

This function only returns on success, see getrusage(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_getrusage_or_die(who, usage);

void explain_message_errno_getrusage	(	char *	message,
		int	message_size,
		int	errnum,
		int	who,
		struct rusage *	usage
	)

The explain_message_errno_getrusage function is used to obtain an explanation of an error returned by the getrusage(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.
who	The original who, exactly as passed to the getrusage(2) system call.
usage	The original usage, exactly as passed to the getrusage(2) system call.

Example:

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

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

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

void explain_message_getrusage	(	char *	message,
		int	message_size,
		int	who,
		struct rusage *	usage
	)

The explain_message_getrusage function is used to obtain an explanation of an error returned by the getrusage(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.
who	The original who, exactly as passed to the getrusage(2) system call.
usage	The original usage, exactly as passed to the getrusage(2) system call.

Example:

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

 if (getrusage(who, usage) < 0)
 {
     char message[3000];
     explain_message_getrusage(message, sizeof(message), who, usage);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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