explain_dup2(3) 					     Library Functions Manual						   explain_dup2(3)

NAME

       explain_dup2 - explain dup2(2) errors

SYNOPSIS

       #include <libexplain/dup2.h>
       const char *explain_dup2(int oldfd, int newfd);
       const char *explain_errno_dup2(int errnum, int oldfd, int newfd);
       void explain_message_dup2(char *message, int message_size, int oldfd, int newfd);
       void explain_message_errno_dup2(char *message, int message_size, int errnum, int oldfd, int newfd);

DESCRIPTION

       These functions may be used to obtain explanations for errors returned by the dup2(2) system call.

   explain_dup2
       const char *explain_dup2(int oldfd, int newfd);

       The  explain_dup2  function  is	used to obtain an explanation of an error returned by the dup2(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 following example:
	      if (dup2(oldfd, newfd) < 0)
	      {
		  fprintf(stderr, "%s
", explain_dup2(oldfd, newfd));
		  exit(EXIT_FAILURE);
	      }

       oldfd   The original oldfd, exactly as passed to the dup2(2) system call.

       newfd   The original newfd, exactly as passed to the dup2(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 buffer across all threads, and many other functions in this library.

   explain_errno_dup2
       const char *explain_errno_dup2(int errnum, int oldfd, int newfd);

       The explain_errno_dup2 function is used to obtain an explanation of an error returned by the dup2(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 following example:
	      if (dup2(oldfd, newfd) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s
", explain_errno_dup2(err, oldfd, newfd));
		  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.

       oldfd   The original oldfd, exactly as passed to the dup2(2) system call.

       newfd   The original newfd, exactly as passed to the dup2(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 buffer across all threads, and many other functions in this library.

   explain_message_dup2
       void explain_message_dup2(char *message, int message_size, int oldfd, int newfd);

       The  explain_message_dup2  function  may  be used to  obtain an explanation of an error returned by the dup2(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 following example:
	      if (dup2(oldfd, newfd) < 0)
	      {
		  char message[3000];
		  explain_message_dup2(message, sizeof(message), oldfd, newfd);
		  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.

       oldfd   The original oldfd, exactly as passed to the dup2(2) system call.

       newfd   The original newfd, exactly as passed to the dup2(2) system call.

   explain_message_errno_dup2
       void explain_message_errno_dup2(char *message, int message_size, int errnum, int oldfd, int newfd);

       The  explain_message_errno_dup2	function  may be used to obtain an explanation of an error returned by the dup2(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 following example:
	      if (dup2(oldfd, newfd) < 0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_dup2(message, sizeof(message), err, oldfd, newfd);
		  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.

       oldfd   The original oldfd, exactly as passed to the dup2(2) system call.

       newfd   The original newfd, exactly as passed to the dup2(2) system call.

SEE ALSO

       dup2(2) duplicate a file descriptor

       explain_dup2_or_die(3)
	       duplicate a file descriptor and report errors

COPYRIGHT

       libexplain version 0.52
       Copyright (C) 2008 Peter Miller

																   explain_dup2(3)