libexplain/errno/wait4.c File Reference

#include <libexplain/common_message_buffer.h>
#include <libexplain/wait4.h>

Go to the source code of this file.

Functions
const char *	explain_errno_wait4 (int errnum, int pid, int *status, int options, struct rusage *rusage)

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Function Documentation

const char* explain_errno_wait4	(	int	errnum,
		int	pid,
		int *	status,
		int	options,
		struct rusage *	rusage
	)

The explain_errno_wait4 function is used to obtain an explanation of an error returned by the wait4(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:

 pid_t pid = wait4(pid, status, options, rusage);
 if (pid < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_wait4(err, pid, status, options,
         rusage));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_wait4_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.
pid	The original pid, exactly as passed to the wait4(2) system call.
status	The original status, exactly as passed to the wait4(2) system call.
options	The original options, exactly as passed to the wait4(2) system call.
rusage	The original rusage, exactly as passed to the wait4(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.

Definition at line 24 of file wait4.c.