The Tcl Shell (Tclsh) provides an interface to the Tcl interpreter that accepts commands from both standard input and text files. Much like the Windows Command Line or Linux Terminal, the Tcl shell allows a developer to rapidly invoke a command and observe the return value or error messages in standard output. The shell differs based on the Operating System in use. For the Unix/Linux systems, this is the standard terminal console; while on a Windows system, the shell is launched separately via an executable.
If invoked with no arguments, the shell interface runs interactively, accepting commands from the native command line. The input line is demarked with a percent sign (%) with the prompt located at the start position. If the shell is invoked from the command line (Windows DOS or Unix/Linux terminal) and arguments are passed, the interpreter will accept the first as the filename to be read. Any additional arguments are processed as variables. The shell will run until the exit
command is invoked or until it has reached the end of the text file.
When invoked with arguments, the shell sets several Tcl variables that may be accessed within your program, much like the C family of languages. These variables are:
Variable |
Explanation |
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This variable contains the number of arguments passed in with the exception of the script file name. A value of 0 is returned if no arguments were passed in. |
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This variable contains a Tcl List with elements detailing the arguments passed in. An empty string is returned if no arguments were provided. |
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This variable contains the filename (if specified) or the name used to invoke the Tcl shell. |
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This variable contains a '1' if Tclsh is running in interactive mode, otherwise a '0' is contained. |
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The |