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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 con-
       tain is the value of strerror(errno), but usually it will do much  bet-
       ter, 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 (dup2(oldfd, newfd) < 0)
	      {
		  fprintf(stderr, "%s\n", 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,  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_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 fol-
       lowing example:
	      if (dup2(oldfd, newfd) < 0)
	      {
		  int err = errno;
		  fprintf(stderr, "%s\n", 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
	       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.

       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, 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_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  fol-
       lowing example:
	      if (dup2(oldfd, newfd) < 0)
	      {
		  char message[3000];
		  explain_message_dup2(message,	sizeof(message), oldfd,	newfd);
		  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.

       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	expla-
       nation 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  fol-
       lowing 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\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.

       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 1.3
       Copyright (C) 2008 Peter	Miller

							       explain_dup2(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

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