Author: dswsis

Tcl have lset command to change value of list’s element.

lset varname index newvalue

Some example of lset on variable named a is presented below.

Lset command can set value of nested list too.

Thats all …

Here is various way to create nested list in tcl. Remember that every thing is a string in Tcl.

% set nestedlist1 { 1 2 { a b c } 3 { d e f } 4 5 }

%set nestedlist2 [list 1 2 [list a b c] 3 [list d e f] 4 5]

%set innerlist1 {a b c}

%set innerlist2 [list d e f]

%set nestedlist3 “1 2 $innerlist1 3 $innerlist2 4 5”

Lindex command can also used to extract an element of nested list.

%lindex $nestedlist1 2 1

b

Try it on tclsh by hand ! Bye …

In Tcl everything is a string. List is also a string. The simplest form of list is a string with zero or more space separated words. Lets set a variable with 3 elements list containing 1,2, and 3.

% set var1 “1 2 3”

% set var2 [list 1 2 3]

% set var3 {1 2 3}

Here we set var1,var2, and var3 to a list, with 3 different way.

To return the number of elements in a list we can use llength command.

% llength $var1

3

To extract an element from list we can use lindex command.

% lindex $var1   1

2

As we can see list has zero based index. The first element is at index 0. Lindex command can accept end and end-? as argument.

% lindex $var1   end

3

% lindex $var1  end-1

2

Thats all for now.

Do you need a Tcl tutorial ? Salvatore write one that we can read online here :

http://www.invece.org/tclwise/

Also check out a n interesting Tcl language implementation here :

http://jim.tcl.tk

Logging application activity to a log file is a best practice to do by a programmer. Here is how we can do it in Tcl scripting language.

Line 1 to 7 is a proc definition named writelog with a parameter. Parameter will contain message to be written to log file located in d:/applogYYYYMMDD.txt based on current date of clock command. Different day will have a different log file.

Line 9 to 17 is some test to writelog. If we pass hello as parameter to writelog command then “YYYY-MM-DD HH:mm:ss : hello” will be written to log file. Every call to writelog will create new line and put current date time on the beginning of line.

Bye!