tclsh(1)

🎀 NAME 🎀

okay bestie, meet tclsh — it's a simple shell containing a Tcl interpreter 💅 this is the tclsh(1) page from the Tcl Applications manual, and we're gonna get you fluent, no cap.

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✨ SYNOPSIS ✨

tclsh ?-encoding name? ?fileName arg arg ...?

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💖 DESCRIPTION 💖

so tclsh is a shell-like application that reads Tcl commands from its standard input or from a file, and then evaluates them. that's the whole vibe. 🦋

if you invoke it with no arguments, it runs interactively — reading Tcl commands from standard input and printing command results and error messages to standard output. it keeps going until you hit the exit command, or until it reaches end-of-file on its standard input. 😭

and here's the lil extra: if there's a file called .tclshrc (or tclshrc.tcl on the Windows platforms) sitting in your home directory, then an interactive tclsh evaluates that file as a Tcl script just before reading the first command from standard input. it's giving "getting ready in the mirror before the party" energy ✨

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🌸 SCRIPT FILES 🌸

if tclsh gets 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 extra arguments get handed to the script as variables (peep the VARIABLES section below 👇). instead of reading commands from standard input, tclsh will read Tcl commands from the named file, and it will exit when it reaches the end of that file.

the end of the file can be marked either by the physical end of the medium, or by the character "\x1A" (control-Z). if that character is present in the file, the tclsh application will read text up to but not including the character. an application that needs that character inside the file may safely encode it as "\x1A", or may generate it by use of commands such as format or binary. 🧚

heads up bestie: 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 it wants to, so it's not a tragedy 💅

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's installed somewhere else then you'll have to modify the line above 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. like, keep it cute and short, okay? 💀

an even better approach is to start your script files with these 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:

1. 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. 🐚
2. it gets around the 30-character file name limit in the previous approach. 👑
3. 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. here's the tea ☕ — sh processes the script first; it treats the second line as a comment and executes the third line. the exec statement causes 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. iconic behavior honestly ✨

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. 🙈

alternatively, you can use /usr/bin/env to locate tclsh on the path, like this:

#!/usr/bin/env tclsh

that has the advantages of being succinct and simple, but the disadvantage of not being flexible in the face of varying names for the binary. pick your fighter 🫶

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💜 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. 🖥️

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🍓 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. so if you're staring at a blank line wondering where your % went — that's why bestie 😭

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🌈 STANDARD CHANNELS 🌈

see Tcl_StandardChannels for more explanations. go read it, i'll wait 💅

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🦋 ZIPFS VIRTUAL FILE SYSTEM 🦋

when a zipfile is concatenated to the end of a tclsh, on startup the contents of the zip archive will be mounted under a virtual file system (VFS). the root of that VFS can be retrieved using the zipfs root command. 🗂️

the zip archive is mounted under the app directory within the VFS.

if a file named main.tcl is present in the top level directory of the zip archive, it will be sourced instead of tclsh's normal command line handing. ✨

if a top level directory tcl_library is present in the zip archive, it will become the directory loaded as env(TCL_LIBRARY). 📁

and yep, if a file named main.tcl is present in the top level directory of the zip archive, it will be sourced instead of the shell's normal command line handling. (she said it twice and honestly? she ate. we love a queen who repeats herself for emphasis 💖)

only one zipfile can be concatenated to the end of executable image (tclsh, or wish). however, if multiple zipfiles are concatenated, only the last one is used. 💀

this filesystem is read-only. files cannot be added or modified within this mounted file system. no editing, no saving, no nothing. 🚫

see zipfs(n) for complete details. 👑

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👀 SEE ALSO 👀

auto_path(n), encoding(n), env(n), fconfigure(n), zipfs(n)

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⭐ KEYWORDS ⭐

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

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and that's the whole page, bestie — this one came straight from the Tcl manual, tclsh(1), and if you made it to the end you are officially the main character of the terminal 🫶💅✨