libexplain/wait.h File Reference

explain wait(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
int	explain_wait_or_die (int *status)
int	explain_wait_on_error (int *status) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_wait (int *status) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_wait (int errnum, int *status) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_wait (char *message, int message_size, int *status)
void	explain_message_errno_wait (char *message, int message_size, int errnum, int *status)

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Detailed Description

explain wait(2) errors

Definition in file wait.h.

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Function Documentation

const char* explain_errno_wait	(	int	errnum,
		int *	status
	)

The explain_errno_wait function is used to obtain an explanation of an error returned by the wait(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:

 int pid = wait(status);
 if (pid < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_wait(err, status));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_wait_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.
status	The original status, exactly as passed to the wait(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.

void explain_message_errno_wait	(	char *	message,
		int	message_size,
		int	errnum,
		int *	status
	)

The explain_message_errno_wait function is used to obtain an explanation of an error returned by the wait(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:

 int pid = wait(status);
 if (pid < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_wait(message, sizeof(message), err, status);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_wait_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.
status	The original status, exactly as passed to the wait(2) system call.

void explain_message_wait	(	char *	message,
		int	message_size,
		int *	status
	)

The explain_message_wait function is used to obtain an explanation of an error returned by the wait(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:

 int pid = wait(status);
 if (pid < 0)
 {
     char message[3000];
     explain_message_wait(message, sizeof(message), status);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_wait_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.
status	The original status, exactly as passed to the wait(2) system call.

const char* explain_wait

(

int *

status

)

The explain_wait function is used to obtain an explanation of an error returned by the wait(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:

 int pid = wait(status);
 if (pid < 0)
 {
     fprintf(stderr, "%s\n", explain_wait(status));
     exit(EXIT_FAILURE);
 }

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

Parameters:

status

The original status, exactly as passed to the wait(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_wait_on_error

(

int *

status

)

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

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

 int pid = explain_wait_on_error(status);
 if (pid < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

status

The status, exactly as to be passed to the wait(2) system call.

Returns:

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

int explain_wait_or_die

(

int *

status

)

The explain_wait_or_die function is used to call the wait(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_wait(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:

 int pid = explain_wait_or_die(status);

Parameters:

status

The status, exactly as to be passed to the wait(2) system call.

Returns:

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