tclsh(1) Tcl Applications tclsh(1)
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NAME
tclsh - Simple shell containing Tcl interpreter
SYNOPSIS
tclsh ?fileName arg arg ...?
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DESCRIPTION
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 com-
mand 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, tclsh evaluates the file as a
Tcl script just before reading the first command from
standard input.
SCRIPT FILES
If tclsh is invoked with arguments then the first argument
is the name of a script file and 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. There is no auto-
matic evaluation of .tclshrc in this case, 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's installed somewhere else then
you'll have to modify the above line to match. Many UNIX
systems do not allow the #! line to exceed about 30 char-
acters 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 "$0" "$@"
This approach has three advantages over the approach in
the previous paragraph. First, the location of the tclsh
binary doesn't 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 previ-
ous approach. Third, this approach will work even if
tclsh is itself a shell script (this is done on some sys-
tems in order to handle multiple architectures or operat-
ing 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 practise 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 disadvan- |
tage of making it harder to write scripts that start up |
uniformly across different versions of Tcl.
VARIABLES
Tclsh sets the following Tcl variables:
argc Contains a count of the number of arg argu-
ments (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 interac-
tively (no fileName was specified and stan-
dard input is a terminal-like device), 0
otherwise.
PROMPTS
When tclsh is invoked interactively it normally prompts
for each command with ``% ''. You can change the prompt
by setting the 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 vari-
able tcl_prompt2 is used in a similar way when a newline
is typed but the current command isn't yet complete; if
tcl_prompt2 isn't set then no prompt is output for incom-
plete commands.
KEYWORDS
argument, interpreter, prompt, script file, shell
Tcl tclsh(1)