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explain_wait4(3)	   Library Functions Manual	      explain_wait4(3)

NAME
       explain_wait4 - explain wait4(2)	errors

SYNOPSIS
       #include	<libexplain/wait4.h>
       const  char  *explain_wait4(int	pid,  int *status, int options,	struct
       rusage *rusage);
       const char *explain_errno_wait4(int errnum, int pid, int	 *status,  int
       options,	struct rusage *rusage);
       void  explain_message_wait4(char	 *message,  int	message_size, int pid,
       int *status, int	options, struct	rusage *rusage);
       void explain_message_errno_wait4(char *message, int  message_size,  int
       errnum, int pid,	int *status, int options, struct rusage	*rusage);

DESCRIPTION
       These  functions	may be used to obtain explanations for errors returned
       by the wait4(2) system call.

   explain_wait4
       const char *explain_wait4(int pid, int  *status,	 int  options,	struct
       rusage *rusage);

       The explain_wait4 function is used to obtain an explanation of an error
       returned	by the wait4(2)	system call.  The least	the message will  con-
       tain  is	the value of strerror(errno), but usually it will do much bet-
       ter, 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 fol-
       lowing example:
	      if (wait4(pid, status, options, rusage) <	0)
	      {
		  fprintf(stderr, "%s\n", explain_wait4(pid, status, options, rusage));
		  exit(EXIT_FAILURE);
	      }

       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, in-
	       cluding other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer across all threads, and many	other functions	in this	library.

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

       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, in-
	       cluding other threads.

       Note: This function is not thread safe, because it shares a return buf-
       fer across all threads, and many	other functions	in this	library.

   explain_message_wait4
       void  explain_message_wait4(char	 *message,  int	message_size, int pid,
       int *status, int	options, struct	rusage *rusage);

       The explain_message_wait4 function may be used to  obtain  an  explana-
       tion  of	 an error returned by the wait4(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  fol-
       lowing example:
	      if (wait4(pid, status, options, rusage) <	0)
	      {
		  char message[3000];
		  explain_message_wait4(message, sizeof(message),
		      pid, status, options, rusage);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       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 re-
	       turned message.

       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.

   explain_message_errno_wait4
       void explain_message_errno_wait4(char *message, int  message_size,  int
       errnum, int pid,	int *status, int options, struct rusage	*rusage);

       The  explain_message_errno_wait4	 function may be used to obtain	an ex-
       planation 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  de-
       tail.

       This  function  is intended to be used in a fashion similar to the fol-
       lowing example:
	      if (wait4(pid, status, options, rusage) <	0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_wait4(message, sizeof(message),	err,
		      pid, status, options, rusage);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       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  re-
	       turned 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.

       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.

SEE ALSO
       wait4(2)
	       wait for	process	to change state

       explain_wait4_or_die(3)
	       wait for	process	to change state	and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

							      explain_wait4(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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