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FREOPEN(3P)                POSIX Programmer's Manual               FREOPEN(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       freopen - open a stream
SYNOPSIS
       #include <stdio.h>
       FILE *freopen(const char *restrict filename, const char *restrict mode,
              FILE *restrict stream);

DESCRIPTION
       The freopen() function shall first attempt  to  flush  the  stream  and
       close  any  file descriptor associated with stream. Failure to flush or
       close the file descriptor successfully shall be ignored. The error  and
       end-of-file indicators for the stream shall be cleared.
       The freopen() function shall open the file whose pathname is the string
       pointed to by filename and associate the stream pointed  to  by  stream
       with it. The mode argument shall be used just as in fopen().
       The  original  stream  shall be closed regardless of whether the subse-
       quent open succeeds.
       If filename is a null pointer, the freopen() function shall attempt  to
       change the mode of the stream to that specified by mode, as if the name
       of the file currently associated with the stream had been used.  It  is
       implementation-defined  which  changes  of mode are permitted (if any),
       and under what circumstances.
       After a successful call to the freopen() function, the  orientation  of
       the  stream shall be cleared,  the encoding rule shall be cleared,  and
       the associated mbstate_t object shall be set  to  describe  an  initial
       conversion state.
       The  largest  value  that  can be represented correctly in an object of
       type off_t shall be established as the offset maximum in the open  file
       description.
RETURN VALUE
       Upon successful completion, freopen() shall return the value of stream.
       Otherwise, a null pointer shall be returned,  and errno shall be set to
       indicate the error.
ERRORS
       The freopen() function shall fail if:
       EACCES Search  permission  is denied on a component of the path prefix,
              or the file exists and the permissions  specified  by  mode  are
              denied,  or  the  file  does  not  exist and write permission is
              denied for the parent directory of the file to be created.
       EINTR  A signal was caught during freopen().
       EISDIR The named file is a directory and mode requires write access.
       ELOOP  A loop exists in symbolic links encountered during resolution of
              the path argument.
       EMFILE {OPEN_MAX}  file  descriptors  are currently open in the calling
              process.
       ENAMETOOLONG
              The length of the filename  argument  exceeds  {PATH_MAX}  or  a
              pathname component is longer than {NAME_MAX}.
       ENFILE The  maximum  allowable number of files is currently open in the
              system.
       ENOENT A component of filename does not name an existing file or  file-
              name is an empty string.
       ENOSPC The  directory  or  file  system that would contain the new file
              cannot be expanded, the file does not exist, and it  was  to  be
              created.
       ENOTDIR
              A component of the path prefix is not a directory.
       ENXIO  The named file is a character special or block special file, and
              the device associated with this special file does not exist.
       EOVERFLOW
              The named file is a regular file and the size of the file cannot
              be represented correctly in an object of type off_t.
       EROFS  The  named  file  resides  on  a  read-only file system and mode
              requires write access.

       The freopen() function may fail if:
       EINVAL The value of the mode argument is not valid.
       ELOOP  More than {SYMLOOP_MAX} symbolic links were  encountered  during
              resolution of the path argument.
       ENAMETOOLONG
              Pathname  resolution of a symbolic link produced an intermediate
              result whose length exceeds {PATH_MAX}.
       ENOMEM Insufficient storage space is available.
       ENXIO  A request was made of a nonexistent device, or the  request  was
              outside the capabilities of the device.
       ETXTBSY
              The  file  is  a pure procedure (shared text) file that is being
              executed and mode requires write access.

       The following sections are informative.
EXAMPLES
   Directing Standard Output to a File
       The following example logs all  standard  output  to  the  /tmp/logfile
       file.

              #include <stdio.h>
              ...
              FILE *fp;
              ...
              fp = freopen ("/tmp/logfile", "a+", stdout);
              ...
APPLICATION USAGE
       The  freopen()  function  is  typically  used  to  attach the preopened
       streams associated with stdin, stdout, and stderr to other files.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       fclose(), fopen(), fdopen(), mbsinit(), the Base Definitions volume  of
       IEEE Std 1003.1-2001, <stdio.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                          FREOPEN(3P)