NAME

freopen − open a stream

SYNOPSIS

#include <stdio.h>

FILE ∗freopen(const char ∗filename, const char ∗mode, FILE ∗stream);

DESCRIPTION

The freopen() function first attempts to flush the stream and close any file descriptor associated with stream. Failure to flush or close the file successfully is ignored. The error and end-of-file indicators for the stream are cleared.

The freopen() function opens the file whose pathname is the string pointed to by filename and associates the stream pointed to by stream with it.  The mode argument is used just as in fopen(3S). 

The original stream is closed regardless of whether the subsequent open succeeds. 

The largest value that can be represented correctly in an object of type off_t will be established as the offset maximum in the open file description. 

RETURN VALUES

Upon successful completion, freopen() returns the value of stream. Otherwise a null pointer is returned and errno is set to indicate the error. 

ERRORS

The freopen() function will 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 Too many symbolic links were encountered in resolving path. 

EMFILE OPEN_MAX file descriptors are currently open in the calling process. 

ENAMETOOLONG
The length of the filename 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 current value of the file position cannot be represented correctly in an object of type fpos_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. 

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 non-existent 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. 

USAGE

The freopen() function is typically used to attach the preopened streams associated with stdin, stdout and stderr to other files.  stderr is by default unbuffered, but the use of freopen() will cause it to become buffered or line-buffered. 

The freopen() function has an explicit 64-bit equivalent.  See interface64(5). 

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

SEE ALSO

fclose(3S), fdopen(3S), fopen(3S), stdio(3S), attributes(5), interface64(5)

SunOS 5.6  —  Last change: 30 Dec 1996