NAME¶
tclsh - Simple shell containing Tcl interpreter
SYNOPSIS¶
tclsh ?
-encoding name? ?
fileName arg arg ...?
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 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 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
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.
VARIABLES¶
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.
PROMPTS¶
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.
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