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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
       Copyright (C) 2008 Peter Miller

AUTHOR

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

                                                            explain_freopen(3)