.\" /*
.\"  * Revision Control Information
.\"  *
.\"  * $Source: /vol/opua/opua2/sis/sis-1.1/common/src/sis/sis_lib/help/RCS/unset.1,v $
.\"  * $Author: sis $
.\"  * $Revision: 1.2 $
.\"  * $Date: 1992/05/06 19:04:01 $
.\"  *
.\"
.XX
set [name] [value]
.X1
unset name ...
.PP
A variable environment is maintained by the command interpreter.
The \fBset\fR command sets a variable to a particular value, and the
\fBunset\fR command removes the definition of a variable.
If \fBset\fR is given no arguments, it prints the definition of all variables.
.PP
Different commands use environment information for different purposes.
The command interpreter makes use of the following:
.TP 8
.B autoexec
Defines a command string to be automatically executed after every command
processed by the command interpreter.
This is useful for things like timing
commands, or tracing the progress of optimization.
.TP 8
.B sisout
Standard output (normally stdout) can be re-directed to a file
by setting the variable sisout.
.TP 8
.B siserr
Standard error (normally stderr) can be re-directed to a file
by setting the variable siserr.
.TP 8
.B open_path
\fBopen_path\fR (in analogy to the shell-variable PATH) is a list of
colon-separated strings giving directories to be searched whenever
a file is opened for read.  Typically the current directory (.) is
first in this list.  The standard system 
library (typically $SIS/sis_lib) is always implicitly appended 
to the current path.
This provides a convenient short-hand
mechanism for reaching standard library files.
.TP 8
.B prompt
defines the prompt string
