Simple shell containing Tcl interpreter
?fileName arg arg ...?
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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, tclsh
evaluates the file as a Tcl script just before reading the
first command from standard input.
argument, interpreter, prompt, script file, shell
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
isn’t yet complete; if tcl_prompt2 isn’t set
then no prompt is output for incomplete commands.
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. 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
’’\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’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 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:
# 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 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 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 disadvantage of
making it harder to write scripts that │ start up uniformly
across different versions of Tcl.
See Tcl_StandardChannels for more explanations.
Tclsh sets the following Tcl variables:
Contains a count of the number of arg arguments (0 if
none), not including the name of the script file.
Contains a Tcl list whose elements are the arg arguments,
in order, or an empty string if there are no arg
Contains fileName if it was specified. Otherwise, contains
the name by which tclsh was invoked.
Contains 1 if tclsh is running interactively (no
fileName was specified and standard input is a
terminal-like device), 0 otherwise.