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explain_getpgrp(3)	   Library Functions Manual	    explain_getpgrp(3)

NAME
       explain_getpgrp - explain getpgrp(2) errors

SYNOPSIS
       #include	<libexplain/getpgrp.h>
       const char *explain_getpgrp(pid_t pid);
       const char *explain_errno_getpgrp(int errnum, pid_t pid);
       void explain_message_getpgrp(char *message, int message_size, pid_t
       pid);
       void explain_message_errno_getpgrp(char *message, int message_size, int
       errnum, pid_t pid);

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

       Note: the getpgrp(2) function has  two  implementations.	  The  POSIX.1
       version	has no arguments, while	the BSD	version	has one	argument.  For
       simplicity of implementation, the argument list seen here includes  the
       pid argument.

       The  POSIX.1  getpgid() semantics can be	obtained by calling getpgrp(0)
       on BSD systems, and this	is the API for	libexplain,  even  on  systems
       that do not use the BSD API.

   explain_getpgrp
       const char *explain_getpgrp(pid_t pid);

       The explain_getpgrp function is used to obtain an explanation of	an er-
       ror returned by the getpgrp(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.

       pid     The  original  pid,  exactly as passed to the getpgrp(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 buf-
       fer 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:
	      pid_t result = getpgrp(pid);
	      if (result < 0)
	      {
		  fprintf(stderr, "%s\n", explain_getpgrp(pid));
		  exit(EXIT_FAILURE);
	      }

       The above code example is available pre-packaged	as  the	 explain_getp-
       grp_or_die(3) function.

   explain_errno_getpgrp
       const char *explain_errno_getpgrp(int errnum, pid_t pid);

       The  explain_errno_getpgrp function is used to obtain an	explanation of
       an error	returned by the	getpgrp(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.

       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  getpgrp(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 buf-
       fer 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:
	      pid_t result = getpgrp(pid);
	      if (result < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_getpgrp(err, pid));
		  exit(EXIT_FAILURE);
	      }

       The  above  code	example	is available pre-packaged as the explain_getp-
       grp_or_die(3) function.

   explain_message_getpgrp
       void explain_message_getpgrp(char *message, int message_size, pid_t
       pid);

       The  explain_message_getpgrp  function is used to obtain	an explanation
       of an error returned by the getpgrp(2) system call. The least the  mes-
       sage  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.

       message The location in which to	store the returned message. If a suit-
	       able 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  getpgrp(2)	system
	       call.

       Example:	 This  function	is intended to be used in a fashion similar to
       the following example:
	      pid_t result = getpgrp(pid);
	      if (result < 0)
	      {
		  char message[3000];
		  explain_message_getpgrp(message, sizeof(message), pid);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The above code example is available pre-packaged	as  the	 explain_getp-
       grp_or_die(3) function.

   explain_message_errno_getpgrp
       void explain_message_errno_getpgrp(char *message, int message_size, int
       errnum, pid_t pid);

       The explain_message_errno_getpgrp function is used to obtain an	expla-
       nation  of  an  error returned by the getpgrp(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 de-
       tail.

       message The location in which to	store the returned message. If a suit-
	       able 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 getpgrp(2)	system
	       call.

       Example:	This function is intended to be	used in	a fashion  similar  to
       the following example:
	      pid_t result = getpgrp(pid);
	      if (result < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_getpgrp(message, sizeof(message), err,
		  pid);
		  fprintf(stderr, "%s\n", message);
		  exit(EXIT_FAILURE);
	      }

       The above code example is available pre-packaged	as  the	 explain_getp-
       grp_or_die(3) function.

SEE ALSO
       getpgrp(2)
	       get process group

       explain_getpgrp_or_die(3)
	       get process group and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2011 Peter	Miller

							    explain_getpgrp(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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