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 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 following example:
	      if (system(command) < 0)
	      {
		  fprintf(stderr, "%s
", 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, 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.

   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  mes-
       sage 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:
	      if (system(command) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s
", 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 neces-
	       sary 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,  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.

   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 explanation 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 following example:
	      if (system(command) < 0)
	      {
		  char message[3000];
		  explain_message_system(message, sizeof(message), command);
		  fprintf(stderr, "%s
", 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 returned 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 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 following example:
	      if (system(command) < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_system(message, sizeof(message), err, command);
		  fprintf(stderr, "%s
", 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 returned message.

       errnum  The error value to be decoded, usually obtained from the errno global variable just before this function is called.  This is neces-
	       sary 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 0.52
       Copyright (C) 2008 Peter Miller

																 explain_system(3)