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explain_waitpid(3)	   Library Functions Manual	    explain_waitpid(3)

NAME
       explain_waitpid - explain waitpid(2) errors

SYNOPSIS
       #include	<libexplain/waitpid.h>
       const char *explain_waitpid(int pid, int	*status, int options);
       const char *explain_errno_waitpid(int errnum, int pid, int *status, int
       options);
       void explain_message_waitpid(char *message, int message_size, int  pid,
       int *status, int	options);
       void explain_message_errno_waitpid(char *message, int message_size, int
       errnum, int pid,	int *status, int options);

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

   explain_waitpid
       const char *explain_waitpid(int pid, int	*status, int options);

       The explain_waitpid function is used to obtain an explanation of	an er-
       ror returned by the waitpid(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 (waitpid(pid, status, options)	< 0)
	      {
		  fprintf(stderr, "%s\n", explain_waitpid(pid, status, options));
		  exit(EXIT_FAILURE);
	      }

       pid     The original pid, exactly as passed to  the  waitpid(2)	system
	       call.

       status  The original status, exactly as passed to the waitpid(2)	system
	       call.

       options The original options, exactly as	passed to the waitpid(2)  sys-
	       tem 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_waitpid
       const char *explain_errno_waitpid(int errnum, int pid, int *status, int
       options);

       The  explain_errno_waitpid function is used to obtain an	explanation of
       an error	returned by the	waitpid(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 (waitpid(pid, status, options)	< 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_waitpid(err,
		      pid, status, options));
		  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 waitpid(2)	system
	       call.

       status  The original status, exactly as passed to the waitpid(2)	system
	       call.

       options The  original options, exactly as passed	to the waitpid(2) sys-
	       tem 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_waitpid
       void  explain_message_waitpid(char *message, int	message_size, int pid,
       int *status, int	options);

       The explain_message_waitpid function may	be used	to  obtain an explana-
       tion of an error	returned by the	waitpid(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 (waitpid(pid, status, options)	< 0)
	      {
		  char message[3000];
		  explain_message_waitpid(message, sizeof(message), pid, status, options);
		  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  waitpid(2)	system
	       call.

       status  The original status, exactly as passed to the waitpid(2)	system
	       call.

       options The original options, exactly as	passed to the waitpid(2)  sys-
	       tem call.

   explain_message_errno_waitpid
       void explain_message_errno_waitpid(char *message, int message_size, int
       errnum, int pid,	int *status, int options);

       The explain_message_errno_waitpid function may be used to obtain	an ex-
       planation  of  an  error	 returned  by the waitpid(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 (waitpid(pid, status, options)	< 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_waitpid(message, sizeof(message), err,
		      pid, status, options);
		  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  waitpid(2)	system
	       call.

       status  The original status, exactly as passed to the waitpid(2)	system
	       call.

       options The original options, exactly as	passed to the waitpid(2)  sys-
	       tem call.

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

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

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

							    explain_waitpid(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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