Originální popis anglicky:
freopen - open a stream
Návod, kniha: POSIX Programmer's Manual
#include <stdio.h>
FILE *freopen(const char *restrict
filename, const
char *restrict mode,
FILE *restrict
stream );
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.
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.
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.
The following example logs all standard output to the
/tmp/logfile file.
#include <stdio.h>
...
FILE *fp;
...
fp = freopen ("/tmp/logfile", "a+", stdout);
...
The
freopen() function is typically used to attach the preopened
streams associated with
stdin,
stdout, and
stderr
to other files.
None.
None.
fclose() ,
fopen() ,
fdopen() ,
mbsinit() , the Base
Definitions volume of IEEE Std 1003.1-2001,
<stdio.h>
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
.
