Tcl

Tcl:   Tool   Command   Language
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Substitutions

$  - Variable Substitution

          Used to substitute the value of a variable

          Eg:    set a 7

                   puts  a                            Output:  a

                   puts  $a                          Output:  7

 

[] – Command Substitution

          Used to substitute expression inside of the brackets

          Eg:    set a 7
                   puts  [expr $a+3]            Output:  10

                   puts  [expr 3 * 5 ]           Output:  15

                   set  c   [expr 2*4] 
                   puts c                             Output: 8
 

\ - Backslash Substitution

          Used to substitute special characters

Comments

Single Line Comment

Single line will be commented by #

Eg:    # This is single line comment

Multiple Lines Comment

Multiple lines will be commented by if with condition 0

Eg:    If 0 {

Comment statement1

Comment statement2

         …………

Comment statementN

                          }

String Representations

When we want to represent multiple strings, we can use either double quotes or curly braces.

Eg:    set str1 “Welcome to Tcl Script”

          puts $str1                                          Output:  Welcome to Tcl Script

          set str2 {Welcome to Tcl Script}

          puts $str2                                          Output:  Welcome to Tcl Script