distrib/share/tcl/help/tcl/intro/tclsh

   1 NAME
   2        tclsh - Simple shell containing Tcl interpreter
   3
   4 SYNOPSIS
   5        tclsh ?fileName arg arg ...?
   6
   7
   8 DESCRIPTION
   9        Tclsh  is  a  shell-like  application  that reads Tcl commands from its
  10        standard input or from a file and evaluates them.  If invoked  with  no
  11        arguments  then  it runs interactively, reading Tcl commands from stan-
  12        dard input and printing command results and error messages to  standard
  13        output.   It runs until the exit command is invoked or until it reaches
  14        end-of-file on its standard input.  If there exists a file .tclshrc (or
  15        tclshrc.tcl  on  the  Windows  platforms)  in the home directory of the
  16        user, tclsh evaluates the file as a Tcl script just before reading  the
  17        first command from standard input.
  18
  19
  20 SCRIPT FILES
  21        If  tclsh is invoked with arguments then the first argument is the name
  22        of a script file and any additional arguments are made available to the
  23        script  as  variables  (see  below).   Instead of reading commands from
  24        standard input tclsh will read Tcl commands from the named file;  tclsh
  25        will exit when it reaches the end of the file.  The end of the file may
  26        be marked either by the physical end of the medium, or by  the  charac-
  27        ter, '\032' ('\u001a', control-Z).  If this character is present in the
  28        file, the tclsh application will read text up to but not including  the
  29        character.  An application that requires this character in the file may
  30        safely encode it as ``\032'', ``\x1a'', or ``\u001a''; or may  generate
  31        it  by use of commands such as format or binary.  There is no automatic
  32        evaluation of .tclshrc when the name of a script file is  presented  on
  33        the  tclsh  command  line,  but the script file can always source it if
  34        desired.
  35
  36        If you create a Tcl script in a file whose first line is
  37               #!/usr/local/bin/tclsh
  38        then you can invoke the script file directly from  your  shell  if  you
  39        mark  the  file  as  executable.   This  assumes  that  tclsh  has been
  40        installed in the default location in /usr/local/bin;  if it's installed
  41        somewhere  else  then  you'll  have  to modify the above line to match.
  42        Many UNIX systems do not allow the #! line to exceed about  30  charac-
  43        ters  in  length,  so be sure that the tclsh executable can be accessed
  44        with a short file name.
  45
  46        An even better approach is to start your script files with the  follow-
  47        ing three lines:
  48               #!/bin/sh
  49               # the next line restarts using tclsh \
  50               exec tclsh "$0" "$@"
  51        This  approach  has  three advantages over the approach in the previous
  52        paragraph.  First, the location of the tclsh binary doesn't have to  be
  53        hard-wired  into  the  script:  it can be anywhere in your shell search
  54        path.  Second, it gets around the 30-character file name limit  in  the
  55        previous  approach.   Third,  this  approach will work even if tclsh is
  56        itself a shell script (this is done on some systems in order to  handle
  57        multiple  architectures or operating systems:  the tclsh script selects
  58        one of several binaries to run).  The three lines  cause  both  sh  and
  59        tclsh  to  process the script, but the exec is only executed by sh.  sh
  60        processes the script first;  it treats the second line as a comment and
  61        executes  the  third  line.  The exec statement cause the shell to stop
  62        processing and instead to  start  up  tclsh  to  reprocess  the  entire
  63        script.   When  tclsh starts up, it treats all three lines as comments,
  64        since the backslash at the end of the second line causes the third line
  65        to be treated as part of the comment on the second line.
  66
  67        You  should  note that it is also common practise to install tclsh with
  68        its version number as part of the name.   This  has  the  advantage  of
  69        allowing  multiple versions of Tcl to exist on the same system at once,
  70        but also the disadvantage of making it harder  to  write  scripts  that
  71        start up uniformly across different versions of Tcl.
  72
  73
  74 VARIABLES
  75        Tclsh sets the following Tcl variables:
  76
  77        argc           Contains  a  count  of the number of arg arguments (0 if
  78                       none), not including the name of the script file.
  79
  80        argv           Contains a Tcl list whose elements  are  the  arg  argu-
  81                       ments,  in order, or an empty string if there are no arg
  82                       arguments.
  83
  84        argv0          Contains fileName if it was specified.  Otherwise,  con-
  85                       tains the name by which tclsh was invoked.
  86
  87        tcl_interactive
  88                       Contains  1  if tclsh is running interactively (no file-
  89                       Name was specified and standard input is a terminal-like
  90                       device), 0 otherwise.
  91
  92
  93 PROMPTS
  94        When  tclsh  is invoked interactively it normally prompts for each com-
  95        mand with ``% ''.  You can change the prompt by setting  the  variables
  96        tcl_prompt1  and  tcl_prompt2.   If variable tcl_prompt1 exists then it
  97        must consist of a Tcl script to output a prompt;  instead of outputting
  98        a  prompt  tclsh will evaluate the script in tcl_prompt1.  The variable
  99        tcl_prompt2 is used in a similar way when a newline is  typed  but  the
 100        current  command  isn't  yet complete; if tcl_prompt2 isn't set then no
 101        prompt is output for incomplete commands.
 102
 103
 104 STANDARD CHANNELS
 105        See Tcl_StandardChannels for more explanations.
 106
 107
 108 SEE ALSO
 109        fconfigure(n), tclvars(n)
 110
 111
 112 KEYWORDS