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explain_system(3)	   Library Functions Manual	     explain_system(3)

NAME
       explain_system -	explain	system(3) errors

SYNOPSIS
       #include	<libexplain/system.h>
       const char *explain_system(const	char *command);
       const char *explain_errno_system(int errnum, const char *command);
       void explain_message_system(char	*message, int message_size, const char
       *command);
       void explain_message_errno_system(char *message,	int message_size,  int
       errnum, const char *command);

DESCRIPTION
       These  functions	may be used to obtain explanations for errors returned
       by the system(3)	system call.

   explain_system
       const char *explain_system(const	char *command);

       The explain_system function is used to obtain an	explanation of an  er-
       ror  returned by	the system(3) 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 (system(command) < 0)
	      {
		  fprintf(stderr, "%s\n", explain_system(command));
		  exit(EXIT_FAILURE);
	      }

       command The original command, exactly as	passed to the system(3)	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_system
       const char *explain_errno_system(int errnum, const char *command);

       The  explain_errno_system  function is used to obtain an	explanation of
       an error	returned by the	system(3) 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 (system(command) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", explain_errno_system(err, command));
		  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.

       command The original command, exactly as	passed to the system(3)	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_system
       void explain_message_system(char	*message, int message_size, const char
       *command);

       The explain_message_system function may be used to  obtain an  explana-
       tion  of	an error returned by the system(3) 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 (system(command) < 0)
	      {
		  char message[3000];
		  explain_message_system(message, sizeof(message), command);
		  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.

       command The original command, exactly as	passed to the system(3)	system
	       call.

   explain_message_errno_system
       void  explain_message_errno_system(char *message, int message_size, int
       errnum, const char *command);

       The explain_message_errno_system	function may be	used to	obtain an  ex-
       planation of an error returned by the system(3) 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 (system(command) < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_system(message,	sizeof(message), err, command);
		  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.

       command The original command, exactly as	passed to the system(3)	system
	       call.

SEE ALSO
       system(3)
	       execute a shell command

       explain_system_or_die(3)
	       execute a shell command and report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

							     explain_system(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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