'\" '\" 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 '\" '\" The definitions below are for supplemental macros used in Tcl/Tk '\" manual entries. '\" '\" .AP type name in/out ?indent? '\" Start paragraph describing an argument to a library procedure. '\" type is type of argument (int, etc.), in/out is either "in", "out", '\" or "in/out" to describe whether procedure reads or modifies arg, '\" and indent is equivalent to second arg of .IP (shouldn't ever be '\" needed; use .AS below instead) '\" '\" .AS ?type? ?name? '\" Give maximum sizes of arguments for setting tab stops. Type and '\" name are examples of largest possible arguments that will be passed '\" to .AP later. If args are omitted, default tab stops are used. '\" '\" .BS '\" Start box enclosure. From here until next .BE, everything will be '\" enclosed in one large box. '\" '\" .BE '\" End of box enclosure. '\" '\" .CS '\" Begin code excerpt. '\" '\" .CE '\" End code excerpt. '\" '\" .VS ?br? '\" Begin vertical sidebar, for use in marking newly-changed parts '\" of man pages. If an argument is present, then a line break is '\" forced before starting the sidebar. '\" '\" .VE '\" End of vertical sidebar. '\" '\" .DS '\" Begin an indented unfilled display. '\" '\" .DE '\" End of indented unfilled display. '\" '\" .SO '\" Start of list of standard options for a Tk widget. The '\" options follow on successive lines, in four columns separated '\" by tabs. '\" '\" .SE '\" End of list of standard options for a Tk widget. '\" '\" .OP cmdName dbName dbClass '\" Start of description of a specific option. cmdName gives the '\" option's name as specified in the class command, dbName gives '\" the option's name in the option database, and dbClass gives '\" the option's class in the option database. '\" '\" .UL arg1 arg2 '\" Print arg1 underlined, then print arg2 normally. '\" '\" SCCS: @(#) man.macros 1.8 96/02/15 20:02:24 '\" '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. .if t .wh -1.3i ^B .nr ^l \n(.l .ad b '\" # Start an argument description .de AP .ie !"\\$4"" .TP \\$4 .el \{\ . ie !"\\$2"" .TP \\n()Cu . el .TP 15 .\} .ie !"\\$3"" \{\ .ta \\n()Au \\n()Bu \&\\$1 \\fI\\$2\\fP (\\$3) .\".b .\} .el \{\ .br .ie !"\\$2"" \{\ \&\\$1 \\fI\\$2\\fP .\} .el \{\ \&\\fI\\$1\\fP .\} .\} .. '\" # define tabbing values for .AP .de AS .nr )A 10n .if !"\\$1"" .nr )A \\w'\\$1'u+3n .nr )B \\n()Au+15n .\" .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n .nr )C \\n()Bu+\\w'(in/out)'u+2n .. .AS Tcl_Interp Tcl_CreateInterp in/out '\" # BS - start boxed text '\" # ^y = starting y location '\" # ^b = 1 .de BS .br .mk ^y .nr ^b 1u .if n .nf .if n .ti 0 .if n \l'\\n(.lu\(ul' .if n .fi .. '\" # BE - end boxed text (draw box now) .de BE .nf .ti 0 .mk ^t .ie n \l'\\n(^lu\(ul' .el \{\ .\" Draw four-sided box normally, but don't draw top of .\" box if the box started on an earlier page. .ie !\\n(^b-1 \{\ \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .el \}\ \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .\} .fi .br .nr ^b 0 .. '\" # VS - start vertical sidebar '\" # ^Y = starting y location '\" # ^v = 1 (for troff; for nroff this doesn't matter) .de VS .if !"\\$1"" .br .mk ^Y .ie n 'mc \s12\(br\s0 .el .nr ^v 1u .. '\" # VE - end of vertical sidebar .de VE .ie n 'mc .el \{\ .ev 2 .nf .ti 0 .mk ^t \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' .sp -1 .fi .ev .\} .nr ^v 0 .. '\" # Special macro to handle page bottom: finish off current '\" # box/sidebar if in box/sidebar mode, then invoked standard '\" # page bottom macro. .de ^B .ev 2 'ti 0 'nf .mk ^t .if \\n(^b \{\ .\" Draw three-sided box if this is the box's first page, .\" draw two sides but no top otherwise. .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .\} .if \\n(^v \{\ .nr ^x \\n(^tu+1v-\\n(^Yu \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c .\} .bp 'fi .ev .if \\n(^b \{\ .mk ^y .nr ^b 2 .\} .if \\n(^v \{\ .mk ^Y .\} .. '\" # DS - begin display .de DS .RS .nf .sp .. '\" # DE - end display .de DE .fi .RE .sp .. '\" # SO - start of list of standard options .de SO .SH "STANDARD OPTIONS" .LP .nf .ta 4c 8c 12c .ft B .. '\" # SE - end of list of standard options .de SE .fi .ft R .LP See the \\fBoptions\\fR manual entry for details on the standard options. .. '\" # OP - start of full description for a single option .de OP .LP .nf .ta 4c Command-Line Name: \\fB\\$1\\fR Database Name: \\fB\\$2\\fR Database Class: \\fB\\$3\\fR .fi .IP .. '\" # CS - begin code excerpt .de CS .RS .nf .ta .25i .5i .75i 1i .. '\" # CE - end code excerpt .de CE .fi .RE .. .de UL \\$1\l'|0\(ul'\\$2 .. .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