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 returns 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 accessed. 

BUGS

Fdopen is not portable to systems other than UNIX. 

7th Edition