tclsh Man page

tclsh Tcl Applications tclsh

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NAME

tclsh – Simple shell containing Tcl interpreter

SYNOPSIS

tclsh ?-encoding name? ?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 stan‐
dard 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.

SCRIPT FILES
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 charac‐
ter 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 follow‐
ing 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.

VARIABLES
Tclsh sets the following global Tcl variables in addition to those cre‐
ated 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 argu‐
ments, in order, or an empty string if there are no arg
arguments.

argv0 Contains fileName if it was specified. Otherwise, con‐
tains the name by which tclsh was invoked.

tcl_interactive
Contains 1 if tclsh is running interactively (no file‐
Name was specified and standard input is a terminal-like
device), 0 otherwise.

PROMPTS
When tclsh is invoked interactively it normally prompts for each com‐
mand with “% ”. You can change the prompt by setting the global vari‐
ables tcl_prompt1 and tcl_prompt2. If variable tcl_prompt1 exists then
it must consist of a Tcl script to output a prompt; instead of out‐
putting 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.

STANDARD CHANNELS
See Tcl_StandardChannels for more explanations.

SEE ALSO

auto_path(3tcl), encoding(3tcl), env(3tcl), fconfigure(3tcl)

KEYWORDS
application, argument, interpreter, prompt, script file, shell

Tcl tclsh

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