subst.n

linux系统下的音频通信

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'\" Copyright (c) 1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\" SCCS: @(#) subst.n 1.9 96/03/25 20:24:17
'\" 
.so man.macros
.TH subst n 7.4 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
subst \- Perform backslash, command, and variable substitutions
.SH SYNOPSIS
\fBsubst \fR?\fB\-nobackslashes\fR? ?\fB\-nocommands\fR? ?\fB\-novariables\fR? \fIstring\fR
.BE

.SH DESCRIPTION
.PP
This command performs variable substitutions, command substitutions,
and backslash substitutions on its \fIstring\fR argument and
returns the fully-substituted result.
The substitutions are performed in exactly the same way as for
Tcl commands.
As a result, the \fIstring\fR argument is actually substituted twice,
once by the Tcl parser in the usual fashion for Tcl commands, and
again by the \fIsubst\fR command.
.PP
If any of the \fB\-nobackslashes\fR, \fB\-nocommands\fR, or
\fB\-novariables\fR are specified, then the corresponding substitutions
are not performed.
For example, if \fB\-nocommands\fR is specified, no command substitution
is performed:  open and close brackets are treated as ordinary characters
with no special interpretation.
.PP
Note: when it performs its substitutions, \fIsubst\fR does not
give any special treatment to double quotes or curly braces.  For
example, the script
.CS
\fBset a 44
subst {xyz {$a}}\fR
.CE
returns ``\fBxyz {44}\fR'', not ``\fBxyz {$a}\fR''.

.SH KEYWORDS
backslash substitution, command substitution, variable substitution