HPUX fdopen[3s]
fopen(3S) fopen(3S)
NAME
fopen(), freopen(), fdopen() - open or re-open a stream file; convert
file to stream
SYNOPSIS
#include <stdio.h>
FILE *fopen(const char *pathname, const char *type);
FILE *freopen(const char *pathname, const char *type, FILE *stream);
FILE *fdopen(int fildes, const char *type);
DESCRIPTION
fopen() Opens the file named by pathname and associates a
stream with it. fopen() returns a pointer to the FILE
structure associated with the stream.
freopen() substitutes the named file in place of the open stream.
The original stream is closed, regardless of whether
the open ultimately succeeds. freopen() returns a
pointer to the FILE structure associated with stream
and makes an implicit call to clearerr() (see
ferror(3S)).
freopen() is typically used to attach the preopened
streams associated with stdin, stdout, and stderr to
other files.
fdopen() associates a stream with a file descriptor. File
descriptors are obtained from open(), dup(), creat(),
or pipe() (see open(2), dup(2), creat(2), and pipe(2)),
which open files but do not return pointers to a FILE
structure stream. Streams are necessary input for many
of the Section (3S) library routines. The type of
stream must agree with the mode of the open file. The
meanings of type used in the fdopen() call are exactly
as specified above, except that w, w+, wb, and wb+ do
not cause truncation of the file.
pathname Points to a character string containing the name of the
file to be opened.
type Character string having one of the following values:
r open for reading
w truncate to zero length or create
for writing
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a append; open for writing at end of
file, or create for writing
rb open binary file for reading
wb truncate to zero length or create
binary file for writing
ab append; open binary file for
writing at end-of-file, or create
binary file
r+ open for update (reading and
writing)
w+ truncate to zero length or create
for update
a+ append; open or create for update
at end-of-file
r+b or rb+ open binary file for update
(reading and writing)
w+b or wb+ truncate to zero length or create
binary file for update
a+b or ab+ append; open or create binary file
for update at end-of-file
When a file is opened for update, both input and output can be done on
the resulting stream. However, output cannot be directly followed by
input without an intervening call to fflush() or to a file positioning
function (fseek(), fsetpos(), or rewind()), and input cannot be
directly followed by output without an intervening call to a file
positioning function unless the input operation encounters end-of-
file.
When a file is opened for append (i.e., when type is a or a+), it is
impossible to overwrite information already in the file. All output
is written at the end of the file, regardless of intervening calls to
fseek(). If two separate processes open the same file for append,
each process can write freely to the file without fear of destroying
output being written by the other. Output from the two processes will
be intermixed in the file in the order in which it is written.
RETURN VALUE
Upon successful completion, fopen(), fdopen(), and freopen() return a
FILE * pointer to the stream. Otherwise, a null pointer is returned
and errno is set to indicate the error.
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fopen(3S) fopen(3S)
ERRORS
fopen(), fdopen(), and freopen() fail if:
[EINVAL] The type argument is not a valid mode.
[ENOMEM] There is insufficient space to allocate a buffer.
fopen() and freopen() fail if:
[EACCES] Search permission is denied on a component of the path
prefix, or the file exists and the permissions
specified by type 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 fopen() or freopen().
function.
[EISDIR] The named file is a directory and type requires write
access.
[EMFILE] The calling process has attempted to exceed its open
file limit.
[ENAMETOOLONG] The length of the pathname string exceeds PATH_MAX or a
pathname component is longer than NAME_MAX while
POSIX_NO_TRUNC is in effect.
[ENFILE] The system file table is full.
[ENOENT] The named file does not exist or the pathname argument
points to 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 the special file
does not exist.
[EROFS] The named file resides on a read-only file system and
type requires write access.
Additional errno values can be set by the underlying open() call made
from the fopen() and freopen() functions (see open(2)).
NOTES
HP-UX binary file types are equivalent to their non-binary
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fopen(3S) fopen(3S)
counterparts. For example, types r and rb are equivalent.
SEE ALSO
creat(2), dup(2), open(2), pipe(2), fclose(3S), fseek(3S), popen(3S),
setvbuf(3S).
STANDARDS CONFORMANCE
fopen(): AES, SVID2, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
fdopen(): AES, SVID2, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1
freopen(): AES, SVID2, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
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