mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-03 09:00:21 +00:00
132 lines
4.4 KiB
Plaintext
132 lines
4.4 KiB
Plaintext
'\"
|
|
'\" Copyright (c) 1993 The Regents of the University of California.
|
|
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
|
|
'\"
|
|
'\" See the file "license.terms" for information on usage and redistribution
|
|
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
|
'\"
|
|
'\" SCCS: @(#) open.n 1.11 96/02/15 20:02:25
|
|
'\"
|
|
.so man.macros
|
|
.TH open n 7.5 Tcl "Tcl Built-In Commands"
|
|
.BS
|
|
'\" Note: do not modify the .SH NAME line immediately below!
|
|
.SH NAME
|
|
open \- Open a file-based or command pipeline channel
|
|
.SH SYNOPSIS
|
|
.sp
|
|
\fBopen \fIfileName\fR
|
|
.br
|
|
\fBopen \fIfileName access\fR
|
|
.br
|
|
\fBopen \fIfileName access permissions\fR
|
|
.BE
|
|
|
|
.SH DESCRIPTION
|
|
.PP
|
|
This command opens a file or command pipeline and returns a channel
|
|
identifier that may be used in future invocations of commands like
|
|
\fBread\fR, \fBputs\fR, and \fBclose\fR.
|
|
If the first character of \fIfileName\fR is not \fB|\fR then
|
|
the command opens a file:
|
|
\fIfileName\fR gives the name of the file to open, and it must conform to the
|
|
conventions described in the \fBfilename\fR manual entry.
|
|
.PP
|
|
The \fIaccess\fR argument, if present, indicates the way in which the file
|
|
(or command pipeline) is to be accessed.
|
|
In the first form \fIaccess\fR may have any of the following values:
|
|
.TP 15
|
|
\fBr\fR
|
|
Open the file for reading only; the file must already exist. This is the
|
|
default value if \fIaccess\fR is not specified.
|
|
.TP 15
|
|
\fBr+\fR
|
|
Open the file for both reading and writing; the file must
|
|
already exist.
|
|
.TP 15
|
|
\fBw\fR
|
|
Open the file for writing only. Truncate it if it exists. If it doesn't
|
|
exist, create a new file.
|
|
.TP 15
|
|
\fBw+\fR
|
|
Open the file for reading and writing. Truncate it if it exists.
|
|
If it doesn't exist, create a new file.
|
|
.TP 15
|
|
\fBa\fR
|
|
Open the file for writing only. The file must already exist, and the file
|
|
is positioned so that new data is appended to the file.
|
|
.TP 15
|
|
\fBa+\fR
|
|
Open the file for reading and writing. If the file doesn't exist,
|
|
create a new empty file.
|
|
Set the initial access position to the end of the file.
|
|
.PP
|
|
In the second form, \fIaccess\fR consists of a list of any of the
|
|
following flags, all of which have the standard POSIX meanings.
|
|
One of the flags must be either \fBRDONLY\fR, \fBWRONLY\fR or \fBRDWR\fR.
|
|
.TP 15
|
|
\fBRDONLY\fR
|
|
Open the file for reading only.
|
|
.TP 15
|
|
\fBWRONLY\fR
|
|
Open the file for writing only.
|
|
.TP 15
|
|
\fBRDWR\fR
|
|
Open the file for both reading and writing.
|
|
.TP 15
|
|
\fBAPPEND\fR
|
|
Set the file pointer to the end of the file prior to each write.
|
|
.TP 15
|
|
\fBCREAT\fR
|
|
Create the file if it doesn't already exist (without this flag it
|
|
is an error for the file not to exist).
|
|
.TP 15
|
|
\fBEXCL\fR
|
|
If \fBCREAT\fR is also specified, an error is returned if the
|
|
file already exists.
|
|
.TP 15
|
|
\fBNOCTTY\fR
|
|
If the file is a terminal device, this flag prevents the file from
|
|
becoming the controlling terminal of the process.
|
|
.TP 15
|
|
\fBNONBLOCK\fR
|
|
.VS
|
|
Prevents the process from blocking while opening the file, and
|
|
possibly in subsequent I/O operations. The exact behavior of
|
|
this flag is system- and device-dependent; its use is discouraged
|
|
(it is better to use the \fBfconfigure\fR command to put a file
|
|
in nonblocking mode).
|
|
For details refer to your system documentation on the \fBopen\fR system
|
|
call's \fBO_NONBLOCK\fR flag.
|
|
.VE
|
|
.TP 15
|
|
\fBTRUNC\fR
|
|
If the file exists it is truncated to zero length.
|
|
.PP
|
|
If a new file is created as part of opening it, \fIpermissions\fR
|
|
(an integer) is used to set the permissions for the new file in
|
|
conjunction with the process's file mode creation mask.
|
|
\fIPermissions\fR defaults to 0666.
|
|
.SH "COMMAND PIPELINES"
|
|
.PP
|
|
If the first character of \fIfileName\fR is ``|'' then the
|
|
remaining characters of \fIfileName\fR are treated as a list of arguments
|
|
that describe a command pipeline to invoke, in the same style as the
|
|
arguments for \fBexec\fR.
|
|
In this case, the channel identifier returned by \fBopen\fR may be used
|
|
to write to the command's input pipe or read from its output pipe,
|
|
depending on the value of \fIaccess\fR.
|
|
If write-only access is used (e.g. \fIaccess\fR is \fBw\fR), then
|
|
standard output for the pipeline is directed to the current standard
|
|
output unless overridden by the command.
|
|
If read-only access is used (e.g. \fIaccess\fR is \fBr\fR),
|
|
standard input for the pipeline is taken from the current standard
|
|
input unless overridden by the command.
|
|
|
|
.SH "SEE ALSO"
|
|
close(n), filename(n), gets(n), read(n), puts(n)
|
|
|
|
.SH KEYWORDS
|
|
access mode, append, create, file, non-blocking, open, permissions,
|
|
pipeline, process
|