term% cat index.txt FOPEN(3S) FOPEN(3S)
NAME
fopen, freopen, fdopen - open a stream
SYNOPSIS
#include <stdio.h>
FILE *fopen(filename, type)
char *filename, *type;
FILE *freopen(filename, type, stream)
char *filename, *type;
FILE *stream;
FILE *fdopen(fildes, type)
char *type;
DESCRIPTION
Fopen opens the file named by filename and associates a stream with it.
Fopen returns a pointer to be used to identify the stream in subsequent
operations.
Type is a character string having one of the following values:
"r" open for reading
"w" create for writing
"a" append: open for writing at end of file, or create for writing
Freopen substitutes the named file in place of the open stream. It re‐
turns the original value of stream. The original stream is closed.
Freopen is typically used to attach the preopened constant names,
stdin, stdout, stderr, to specified files.
Fdopen associates a stream with a file descriptor obtained from open,
dup, creat, or pipe(2). The type of the stream must agree with the
mode of the open file.
SEE ALSO
open(2), fclose(3)
DIAGNOSTICS
Fopen and freopen return the pointer NULL if filename cannot be ac‐
cessed.
BUGS
Fdopen is not portable to systems other than UNIX.
FOPEN(3S)