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 subsequent 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 filename 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 .