- NAME
- tclsh — Simple shell containing Tcl interpreter
- SYNOPSIS
- DESCRIPTION
- SCRIPT FILES
- VARIABLES
- argc
- argv
- argv0
- tcl_interactive
- PROMPTS
- STANDARD CHANNELS
- SEE ALSO
- KEYWORDS
tclsh — Simple shell containing Tcl interpreter
tclsh ?-encoding name? ?fileName arg arg ...?
Tclsh is a shell-like application that reads Tcl commands
from its standard input or from a file and evaluates them.
If invoked with no arguments then it runs interactively, reading
Tcl commands from standard input and printing command results and
error messages to standard output.
It runs until the exit command is invoked or until it
reaches end-of-file on its standard input.
If there exists a file .tclshrc (or tclshrc.tcl on
the Windows platforms) in the home directory of
the user, interactive tclsh evaluates the file as a Tcl script
just before reading the first command from standard input.
If tclsh is invoked with arguments then the first few arguments
specify the name of a script file, and, optionally, the encoding of
the text data stored in that script file. Any additional arguments
are made available to the script as variables (see below).
Instead of reading commands from standard input tclsh will
read Tcl commands from the named file; tclsh will exit
when it reaches the end of the file.
The end of the file may be marked either by the physical end of
the medium, or by the character,
“\032”
(“\u001a”, control-Z).
If this character is present in the file, the tclsh application
will read text up to but not including the character. An application
that requires this character in the file may safely encode it as
“\032”,
“\x1A”,
or
“\u001a”;
or may generate it by use of commands such as format or binary.
There is no automatic evaluation of .tclshrc when the name
of a script file is presented on the tclsh command
line, but the script file can always source it if desired.
If you create a Tcl script in a file whose first line is
#!/usr/local/bin/tclsh
then you can invoke the script file directly from your shell if
you mark the file as executable.
This assumes that tclsh has been installed in the default
location in /usr/local/bin; if it is installed somewhere else
then you will have to modify the above line to match.
Many UNIX systems do not allow the #! line to exceed about
30 characters in length, so be sure that the tclsh
executable can be accessed with a short file name.
An even better approach is to start your script files with the
following three lines:
#!/bin/sh
# the next line restarts using tclsh \
exec tclsh "$0" ${1+"$@"}
This approach has three advantages over the approach in the previous
paragraph. First, the location of the tclsh binary does not have
to be hard-wired into the script: it can be anywhere in your shell
search path. Second, it gets around the 30-character file name limit
in the previous approach.
Third, this approach will work even if tclsh is
itself a shell script (this is done on some systems in order to
handle multiple architectures or operating systems: the tclsh
script selects one of several binaries to run). The three lines
cause both sh and tclsh to process the script, but the
exec is only executed by sh.
sh processes the script first; it treats the second
line as a comment and executes the third line.
The exec statement cause the shell to stop processing and
instead to start up tclsh to reprocess the entire script.
When tclsh starts up, it treats all three lines as comments,
since the backslash at the end of the second line causes the third
line to be treated as part of the comment on the second line.
You should note that it is also common practice to install tclsh with
its version number as part of the name. This has the advantage of
allowing multiple versions of Tcl to exist on the same system at once,
but also the disadvantage of making it harder to write scripts that
start up uniformly across different versions of Tcl.
Tclsh sets the following global Tcl variables in addition to those
created by the Tcl library itself (such as env, which maps
environment variables such as PATH into Tcl):
- argc
-
Contains a count of the number of arg arguments (0 if none),
not including the name of the script file.
- argv
-
Contains a Tcl list whose elements are the arg arguments,
in order, or an empty string if there are no arg arguments.
- argv0
-
Contains fileName if it was specified.
Otherwise, contains the name by which tclsh was invoked.
- tcl_interactive
-
Contains 1 if tclsh is running interactively (no
fileName was specified and standard input is a terminal-like
device), 0 otherwise.
When tclsh is invoked interactively it normally prompts for each
command with
“% ”.
You can change the prompt by setting the global
variables tcl_prompt1 and tcl_prompt2. If variable
tcl_prompt1 exists then it must consist of a Tcl script
to output a prompt; instead of outputting a prompt tclsh
will evaluate the script in tcl_prompt1.
The variable tcl_prompt2 is used in a similar way when
a newline is typed but the current command is not yet complete;
if tcl_prompt2 is not set then no prompt is output for
incomplete commands.
See Tcl_StandardChannels for more explanations.
auto_path, encoding, env, fconfigure
application, argument, interpreter, prompt, script file, shell
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.