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Standard C Library Functionsfdopen(3C)


NAME

 fdopen - associate a stream with a file descriptor

SYNOPSIS

 
#include <stdio.h>
FILE *fdopen(int fildes, const char *mode);

DESCRIPTION

 

The fdopen() function associates a stream with a file descriptor fildes.

The mode argument is a character string having one of the following values:

r or rbOpen a file for reading.
w or wbOpen a file for writing.
a or abOpen a file for writing at end of file.
r+ or rb+ or r+bOpen a file for update (reading and writing).
w+ or wb+ or w+bOpen a file for update (reading and writing).
a+ or ab+ or a+bOpen a file for update (reading and writing) at end of file.

The meaning of these flags is exactly as specified for the fopen(3C) function, except that modes beginning with w do not cause truncation of the file.

The mode of the stream must be allowed by the file access mode of the open file. The file position indicator associated with the new stream is set to the position indicated by the file offset associated with the file descriptor.

The fdopen() function preserves the offset maximum previously set for the open file description corresponding to fildes.

The error and end-of-file indicators for the stream are cleared. The fdopen() function may cause the st_atime field of the underlying file to be marked for update.

If fildes refers to a shared memory object, the result of the fdopen() function is unspecified.

RETURN VALUES

 

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

The fdopen() function may fail and not set errno if there are no free stdio streams.

ERRORS

 

The fdopen() function may fail if:

EBADF
The fildes argument is not a valid file descriptor.
EINVAL
The mode argument is not a valid mode.
EMFILE
The number of streams currently open in the calling process is either FOPEN_MAX or STREAM_MAX.
ENOMEM
Insufficient space to allocate a buffer.

USAGE

 

The number of streams that a process can have open at one time is STREAM_MAX. If defined, it has the same value as FOPEN_MAX.

File descriptors are obtained from calls like open(2), dup(2), creat(2) or pipe(2), which open files but do not return streams. Streams are necessary input for almost all of the Section 3S library routines.

ATTRIBUTES

 

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

ATTRIBUTE TYPEATTRIBUTE VALUE
MT-LevelMT-Safe

SEE ALSO

 

creat(2), dup(2), open(2), pipe(2), fclose(3C), fopen(3C), attributes(5)


SunOS 5.9Go To TopLast Changed 30 Dec 1996

 
      
      
Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.