NAME

       explain_freopen - explain freopen(3) errors

SYNOPSIS

       #include <libexplain/freopen.h>
       const char *explain_freopen(const char *pathname, const char *flags, FILE *fp);
       const  char  *explain_errno_freopen(int  errnum,  const char *pathname, const char *flags,
       FILE *fp);
       void explain_message_freopen(char *message, int message_size, const char *pathname,  const
       char *flags, FILE *fp);
       void explain_message_errno_freopen(char *message, int message_size, int errnum, const char
       *pathname, const char *flags, FILE *fp);

DESCRIPTION

       These functions may be used to obtain explanations for freopen(3) errors.

   explain_freopen
       const char *explain_freopen(const char *pathname, const char *flags, FILE *fp);

       The explain_freopen function is used to obtain an explanation of an error returned by  the
       freopen(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 (!freopen(pathname, flags, fp))
              {
                  fprintf(stderr, '%s0, explain_freopen(pathname, flags, fp));
                  exit(EXIT_FAILURE);
              }

       pathname
               The original pathname, exactly as passed to the freopen(3) system call.

       flags   The original flags, exactly as passed to the freopen(3) system call.

       fp      The original fp, exactly as passed to the freopen(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_freopen
       const  char  *explain_errno_freopen(int  errnum,  const char *pathname, const char *flags,
       FILE *fp);

       The explain_errno_freopen function is used to obtain an explanation of an  error  returned
       by  the  freopen(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 (freopen(pathname, flags, fp))
              {
                  int err = errno;
                  fprintf(stderr, '%s0, explain_errno_freopen(err, pathname,
                      flags, fp));
                  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.

       pathname
               The original pathname, exactly as passed to the freopen(3) system call.

       flags   The original flags, exactly as passed to the freopen(3) system call.

       fp      The original fp, exactly as passed to the freopen(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_freopen
       void explain_message_freopen(char *message, int message_size, const char *pathname,  const
       char *flags, FILE *fp);

       The explain_message_freopen function is used to obtain an explanation of an error returned
       by the freopen(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 (!freopen(pathname, flags, fp))
              {
                  char message[3000];
                  explain_message_freopen(message, sizeof(message), pathname, flags,
                      fp);
                  fprintf(stderr, '%s0, message);
                  exit(EXIT_FAILURE);
              }

       message The location in which to store the returned message.   Because  a  message  return
               buffer has been supplied, this function is thread safe.

       message_size
               The size in bytes of the location in which to store the returned message.

       pathname
               The original pathname, exactly as passed to the freopen(3) system call.

       flags   The original flags, exactly as passed to the freopen(3) system call.

       fp      The original fp, exactly as passed to the freopen(3) system call.

   explain_message_errno_freopen
       void explain_message_errno_freopen(char *message, int message_size, int errnum, const char
       *pathname, const char *flags, FILE *fp);

       The explain_message_errno_freopen function is used to obtain an explanation  of  an  error
       returned  by  the freopen(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 (!freopen(pathname, flags, fp))
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_freopen(message, sizeof(message), err,
                      pathname, flags, fp);
                  fprintf(stderr, '%s0, message);
                  exit(EXIT_FAILURE);
              }

       message The  location  in  which  to store the returned message.  Because a message return
               buffer has been 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.

       pathname
               The original pathname, exactly as passed to the freopen(3) system call.

       flags   The original flags, exactly as passed to the freopen(3) system call.

       fp      The original fp, exactly as passed to the freopen(3) system call.

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2008 Peter Miller

AUTHOR

       Written by Peter Miller <pmiller@opensource.org.au>

                                                                               explain_freopen(3)