- 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.