Tcl / Tk Tutorial

1. Tcl/TkTutorial Dongsoo S. Kim dskim@iupui.edu

2. What is Tcl/Tk? • Tcl: Tool Command Language • Interpreted programming (scripting) language • Build on-the-fly commands and procedures • Embeddable • Platform-independent • Tk: • GUI toolkit and widgets based on Tcl • Open source, cross-platform

3. Why Tcl/TK? • Easy and fast programming • Free • Lots of online documentation, mostly free • Resources • http://www.tcl.tk • Major applications use the Tcl as their interfaces: • Ns2 • Mentor Graphics

4. Hello World % tcl tcl>puts "Hello. World!" Hello. World! tcl>exit %

5. Script File • Start the Tcl program followed by a filename containing the script. % cat hello.tcl puts "Hello. World!" % tcl hello.tcl Hello. World! %

6. Script as a Program • A script text file can be considered as a program if • it is an executable file, and • its first line contains a full path name of the tcl program following “#!” % ls -l -rwxr-xr-x 1 user group 42 Jul 3 13:12 hello.tcl % which tcl /usr/local/bin/tcl % cat hello.tcl #!/usr/local/bin/tcl puts "Hello. World!" % hello.tcl Hello. World! %

7. Tcl Syntax • Simple syntax • command_name arg1 arg2 … • Print to screen (puts) puts –nonewline"Hello. " puts "World!" • Assignment (set) set income 32000 puts "The income is $income" • Use '$' to get the value of a variable (R-value)

8. Comments • A line started with a pond sign(#) is ignored as comments until the end of the line • A command can be followed by a comment in a line with by placing ;# • Exception • #! at the first line indicates the script program • It is a Unix rule, but not a Tcl rule # the first script puts –nonewline"Hello. " ;# continuing puts "World!“

9. Multiple Commands in a Line • A Tcl command is terminated by an invisible new line character, or • A semicolon(;) can be used to explicitly terminate a command tcl>puts "Hello. "; puts "World! " hello world

10. A Command Stretched to Lines • A command can be stretched to multiple lines by using backslashes (\) • The backslash and a following new line character is ignored • Note: There must not be any characters (even space characters) between the backslash and the new line character tcl>puts -nonewline \ =>"Hello. World!" Hello. World!tcl>

11. Mathematical Expression Tcl>set pi 3.141592 Tcl>set r 2 Tcl>expr 2*$pi*$r 12.566368 Tcl>expr sin($pi/3) 0.866025294853 • Mathematical expression command (expr) • Operators • arithmetic (+, -, *, /, %) • Bitwise (~, <<, >>, &, ^, |) • Logical (!, &&, ||) • Boolean (<, >, <=, >=, ==, !=) • String Boolean (eq, ne, <, >, <=, >=) • List containment (in, ni) • Ternary (x?y:z) • Math functions (log, sin, cos, …)

12. Sub-Command Evaluation tcl>set a 3.0 tcl>set b $a+4 tcl>puts $b 3.0+4 tcl>set c [expr $a+4] tcl>puts $c 7.0 • A Tcl command in a Tcl command: []

13. Control Structures (if) set sel 3 if {$sel == 1} { puts "Selection $sel" } elseif {$sel == 2} { puts "Selection $sel" } else { puts "Invalid selection" } • if {cond} {commands}[ elseif {cond} {commands} …][ else {commands} ]

14. Control Structures (while) set i 1 set sum 0 while {$i <= 10} { set sum [expr $sum+$i] incri } while {cond} {commands}

15. Control Structures (for) puts "Fahrenheit\tCelcius" for {set fahr 0} {$fahr < 100} {incrfahr} { set celc [expr 5*($fahr-32)/9] puts "$fahr\t\t$celc" } Fahrenheit Celcius 0 -18 1 -182 -17 … for {init} {term} {incr} {statements}

16. Control Structures (foreach) • Basic foreachset weekdays {Sun Mon Tue Wed Thu Fri Sat}foreach d $weekdays { puts $d} • foreach Variationsset Colors {red orange yellow green blue purple}foreach {a b c} $Colors { puts "$c--$b--$a“}set Foods {apple orange banana lime berry grape}foreach f $Foods c $Colors { puts "a $f is usually $c" } foreach {a b} $Foods c $Colors { puts "$a & $b are foods. $c is a color." }

17. Procedures proc mile2km dist { return [expr $dist*1.6] } puts "Miles \t KM" for {set d 1} {$d < 10} {incr d} { set km [mile2km $d] puts "$d\t $km" } • Called by value only • Syntaxprocname arg-list proc-body

18. Variable scope • set a 5 set b 6 set c 7 proc var_scope { } { global a set a 3 set b 2 set ::c 1 } var_scope puts "The value for a b c is: $a $b $c" By default, all variables in a procedure are local. To access the variable outside of the scope, use the command “global”.

19. Lists in Tcl • set my_list [list a b c] set my_list "a b c " set my_list {a b c} An ordered collection of elements A string containing any number of elements separated by white spaces (space or tab characters). For example, Sun Mon Tue Wed Thu Fri Satis a list with four element. To save a list to a variable

20. List Operations concat – join multiple list into a single list join – concatenate list elements into a string lappend – append elements to an existing list lindex – return an indexed element from a list linsert – insert an element to an existing list list – create explicitly a list from values llength – return the number of elements in a list lrange – return a sub-list from a list lreplace – return a new list after replacing elements lsearch – return the index of a searching pattern lsort – sort the list split – return a list by splitting a string by a split-char.

21. List Operations, Example set weekday [list “Mon” “Tue” “Wed” “Thu” “Fri”] set weekend {Sat Sun} set week [concat $weekday $weekend] puts $week • Mon Tue Wed Thu Fri Sat Sun lindex $week 0 • Mon • lindex $week end • Sun • llength $weekday • 5

22. Lists of lists (of lists…) set a [list [list x y z]] puts [lindex $a 0] puts [lindex [lindex $a 0] 1] puts [lindex [lindex $a 1] 0] (unexpected result) set a [list x [list [list y] [list z]]] => How to get to the z? set arg1 [list g [list f [list h [list i X]]] [list r Y] k] set arg2 [list g [list f [list h [list i Y]]] [list r b] L] set both [list $arg1 $arg2] puts $both

23. Array operations Associative arrays (string as index) set color(rose) red set color(sky) blue set color(medal) gold set color(leaves) green set color(blackboard) black puts [array exists color](tests if an array with the name "color" exists) puts [array exists colour] puts [array names color] (returns a list of the index strings) foreach item [array names color] { puts "$item is $color($item)" } (iterating through array) set lstColor [array get color] (convert array to list) array set color $lstColor (convert list to array)

24. Regular expressions • regsubset stmt "Fan is one of Shania’s fans" regsub –nocase"fan" $stmt "Kristy"newStmt ?switches? exp string subSpec ?varName? puts "$newStmt" regsub –nocase –all "fan" $stmt "Kristy"newStmt puts "$newStmt" • regexp(returns 1 if the regular expression matches the string, else returns 0) puts [regexp –nocase"fan" $stmt] ?switches? regexp string • format puts [format "%s is a %d-year-old" Fan 26] formatString ?argarg ...?

25. String operations set statement " Fan is a student " set statement [string trim $statement] puts [string length $statement] puts [string length statement] puts [string index $statement 4] puts [string index $statement end] puts [string first"is" $statement] (string last) puts [string first $statement "is"] puts [string range $statement 4 end] puts [string replace $statement 9 end "professor"] puts [string match"*student" $statement] (* ? [])

26. File Operations set fRead [open source.txt r] set fWrite [open target.txt w] while {![eof $fRead]} { set strLine [gets $fRead] ;#or gets $fReadstrLine regsub –nocase –all "fan" $strLine"kristy" strLine puts $fWrite $strLine } close $fRead close $fWrite ################ source.txt ################ Fan is a CSE student. Fan is also one of Shania’s fans. Kristy and Fan are classmates.

27. Miscellaneous commands • eval: execute a command dynamically built up in your program set Script { set Number1 17 set Number2 25 set Result [expr $Number1 + $Number2] } eval $Script • exec: execute external programs • clock • trace • info • after