This article describes how to write and execute a "Hello World" tclsh script on Linux (Fedora).

1. the prerequisites

• a text editor of your choice (e.g. vi)
• tclsh - Simple shell containing Tcl interpreter

make sure you have installed the bash shell:

#  [root@fedora12 Desktop]# rpm -q tcl
tcl-8.5.7-4.fc12.i686

If it is not installed yet, you can install it with yum (you need to be root to do that):

# yum install tcl

2. write the code

open an empty file with a text editor (e.g. vi):

# vi helloworld.sh

#!/bin/sh
# the next line restarts using tclsh \
exec tclsh "$0" "$@"

puts "Hello World!"

explanation

#!/bin/sh

This tells the system to use the /bin/sh interpreter to execute the script. You can find out the full path of your sh interpreter by entering the following command:

# which sh
/bin/sh

# the next line restarts using tclsh \
exec tclsh "$0" "$@"

from the man page:

"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."

puts "Hello World!"

{/chilicode}

prints the string "Hello World!"

3. make the script executable

# chmod u+x helloworld.sh

4. run the program

you can now execute the script program with:

# ./helloworld.sh
Hello World!

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