path: root/usr/src/man/man3c/fdopen.3c

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.TH FDOPEN 3C "Apr 18, 2006"
.SH NAME
fdopen \- associate a stream with a file descriptor
.SH SYNOPSIS
.LP
.nf
#include <stdio.h>

\fBFILE *\fR\fBfdopen\fR(\fBint\fR \fIfildes\fR, \fBconst char *\fR\fImode\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBfdopen()\fR function associates a stream with a file descriptor
\fIfildes\fR.
.sp
.LP
The \fImode\fR argument is a character string having one of the following
values:
.sp

.sp
.TS
l l
l l .
\fBr\fR or \fBrb\fR	Open a file for reading.
\fBw\fR or \fBwb\fR	Open a file for writing.
\fBa\fR or \fBab\fR	Open a file for writing at end of file.
\fBr+\fR, \fBrb+\fR or \fBr+b\fR	T{
Open a file for update (reading and writing).
T}
\fBw+\fR, \fBwb+\fR or \fBw+b\fR	T{
Open a file for update (reading and writing).
T}
\fBa+\fR, \fBab+\fR or \fBa+b\fR	T{
Open a file for update (reading and writing) at end of file.
T}
.TE

.sp
.LP
The meaning of these flags is exactly as specified for the \fBfopen\fR(3C)
function, except that modes beginning with \fIw\fR do not cause truncation of
the file. A trailing \fBF\fR character can also be included in the \fImode\fR
argument as described in \fBfopen\fR(3C) to enable extended FILE facility.
.sp
.LP
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.
.sp
.LP
The \fBfdopen()\fR function preserves the offset maximum previously set for the
open file description corresponding to  \fIfildes\fR.
.sp
.LP
The error and end-of-file indicators for the stream are cleared. The
\fBfdopen()\fR function may cause the \fBst_atime\fR field of the underlying
file to be marked for update.
.sp
.LP
If \fIfildes\fR refers to a shared memory object, the result of the
\fBfdopen()\fR function is unspecified.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBfdopen()\fR returns a pointer to a stream.
Otherwise, a null pointer is returned and \fBerrno\fR is set to indicate the
error.
.sp
.LP
The \fBfdopen()\fR function may fail and not set \fBerrno\fR if there are no
free \fBstdio\fR streams.
.SH ERRORS
.sp
.LP
The \fBfdopen()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The \fIfildes\fR argument is not a valid file descriptor.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fImode\fR argument is not a valid mode.
.RE

.sp
.ne 2
.na
\fB\fBEMFILE\fR\fR
.ad
.RS 10n
{\fBFOPEN_MAX\fR} streams are currently open in the calling process.
.sp
{\fBSTREAM_MAX\fR} streams are currently open in the calling process.
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
There is insufficient space to allocate a buffer.
.RE

.SH USAGE
.sp
.LP
A process is allowed to have at least {\fBFOPEN_MAX\fR} \fBstdio\fR streams
open at a time. For 32-bit applications, however, the underlying ABIs formerly
required that no file descriptor used to access the file underlying a
\fBstdio\fR stream have a value greater than 255. To maintain binary
compatibility with earlier Solaris releases, this limit still constrains 32-bit
applications.
.sp
.LP
File descriptors are obtained from calls like \fBopen\fR(2), \fBdup\fR(2),
\fBcreat\fR(2) or \fBpipe\fR(2), which open files but do not return streams.
Streams are necessary input for almost all of the standard I/O library
functions.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	See below.
_
MT-Level	MT-Safe
.TE

.sp
.LP
The \fBF\fR character in the \fImode\fR argument is Evolving. In all other
respects this function is Standard.
.SH SEE ALSO
.sp
.LP
\fBcreat\fR(2), \fBdup\fR(2), \fBopen\fR(2), \fBpipe\fR(2), \fBfclose\fR(3C),
\fBfopen\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)