tclsh8.5
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 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.
keywords
argument, interpreter, prompt, script file, shell
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
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.
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
#!/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.
standard channels
See Tcl_StandardChannels for more explanations.
variables
Tclsh sets the following Tcl variables:
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.
see also
encoding(3tcl),
fconfigure(3tcl), tclvars(3tcl)