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 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 (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,
               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_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 following 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,
               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_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 explanation 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 following 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 returned 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 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 following 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 returned 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 1.4
       Copyright (C) 2008 Peter Miller

                                                                                 explain_fcntl(3)