Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
explain_fcntl(3)	   Library Functions Manual	      explain_fcntl(3)

NAME
       explain_fcntl - explain fcntl(2)	errors

SYNOPSIS
       #include	<libexplain/fcntl.h>
       const char *explain_fcntl(int fildes, int command, long arg);
       const  char  *explain_errno_fcntl(int  errnum, int fildes, int command,
       long arg);
       void explain_message_fcntl(char *message, int message_size, int fildes,
       int command, long arg);
       void  explain_message_errno_fcntl(char  *message, int message_size, int
       errnum, int fildes, int command,	long arg);

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

   explain_fcntl
       const char *explain_fcntl(int fildes, int command, long arg);

       The explain_fcntl function is used to obtain an explanation of an error
       returned	by the fcntl(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 (fcntl(fildes,	command, arg) <	0)
	      {
		  fprintf(stderr, "%s\n", explain_fcntl(fildes,	command, arg));
		  exit(EXIT_FAILURE);
	      }

       fildes  The original fildes, exactly as passed to the  fcntl(2)	system
	       call.

       command The  original command, exactly as passed	to the fcntl(2)	system
	       call.

       arg     The original arg, exactly as  passed  to	 the  fcntl(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_fcntl
       const char *explain_errno_fcntl(int errnum, int	fildes,	 int  command,
       long arg);

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

       fildes  The  original  fildes, exactly as passed	to the fcntl(2)	system
	       call.

       command The original command, exactly as	passed to the fcntl(2)	system
	       call.

       arg     The  original  arg,  exactly  as	 passed	to the fcntl(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_fcntl
       void explain_message_fcntl(char *message, int message_size, int fildes,
       int command, long arg);

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

       fildes  The original fildes, exactly as passed to the  fcntl(2)	system
	       call.

       command The  original command, exactly as passed	to the fcntl(2)	system
	       call.

       arg     The original arg, exactly as  passed  to	 the  fcntl(2)	system
	       call.

   explain_message_errno_fcntl
       void  explain_message_errno_fcntl(char  *message, int message_size, int
       errnum, int fildes, int command,	long arg);

       The explain_message_errno_fcntl function	may be used to obtain  an  ex-
       planation  of an	error returned by the fcntl(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 de-
       tail.

       This function is	intended to be used in a fashion similar to  the  fol-
       lowing example:
	      if (fcntl(fildes,	command, arg) <	0)
	      {
		  int err = errno;
		  char message[3000];
		  explain_message_errno_fcntl(message, sizeof(message),	err, fildes,
		      command, arg);
		  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.

       fildes  The original fildes, exactly as passed to the  fcntl(2)	system
	       call.

       command The  original command, exactly as passed	to the fcntl(2)	system
	       call.

       arg     The original arg, exactly as  passed  to	 the  fcntl(2)	system
	       call.

SEE ALSO
       fcntl(2)
	       manipulate a file descriptor

       explain_fcntl_or_die(3)
	       manipulate a file descriptor and	report errors

COPYRIGHT
       libexplain version 1.3
       Copyright (C) 2008 Peter	Miller

							      explain_fcntl(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=explain_fcntl&sektion=3&manpath=FreeBSD+12.2-RELEASE+and+Ports>

home | help