Tcl ProgrammingCyberDaemons
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AgendaTcl (List)
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TCL Tcl Tool Control Language Tk Tcl(Extension) GUI Tcl shell
script C tk buttons menuslistboxes scrollbars Tcl Basic Tcl Script
Tcl Tcl Script Tcl tclsh Tcl (Extension)
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Tcl John K. Ousterhout 1988 Tcl/Tk Tk 1989 1991 Tk usable around
1992 see http://www.tcl.tk/doc/tclHistory.html
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Tcl high-level scripting language less code than Motif or
Win32
most platforms Unix, Mac, Windows hides UI, system call
differences
interpreted execute directly, without compiling or linking
autoloading automatically load libraries
extensible commands in Tcl or C
free source no royalties
embeddable Tcl interpreter callable from CTango Training 5
Tcl
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tcltclsh$ tclsh % set x 7 7
wish$ wish % button .b text Hello command exit % pack .b
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tclC#include main(int argc, char *argv[]) { Tcl_interp *interp =
Tcl_CreateInterp(); code = Tcl_EvalFile(interp, argv[1]); if
(*interp->result != 0) { printf(%s\n, interp->result); }
}Tango Training 8
TCLhello.tcl:set s "Hello World" puts $s Command: $tclsh
hello.tcl Result: tclsh (tclsh) Hello World
or tcl
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Tcl Everything is a list of words no fixed grammarfirst word is
command
{} delay evaluation, may nest "" only needed when spaces: set x
"foo" = set x foo
everything can be done dynamically: new procedures, variables,
name spaces, ... interpreter model, but internally compiled into
bytecodeTango Training 10
(variable)setEx.: set a 101
unsetEx.: unset a
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(variable substituion) variable substitution: set a 17 command
substitution, evaluated as separate script: set b [expr $a*4]
backslash substitution: set x \$a
set b 18 set a [expr $b+2] set a "b-3 is [expr $b-3]"Tango
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18 20 b-3 is 1512
incr increments variable append adds strings to end: append msg
"more text" argv variable is list of command line arguments env is
list of environment variables
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(Math expressions) expr : expr arg ?arg arg ...?
:if {$x == $y} { ...}set x [expr {$x + 7}] set y [expr
{log($y)}][]
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set b 5 expr ($b*4) - 3 expr $b = 90} { puts "Your level is A" }
elseif {$grade < 90} { puts "Your level isnt A" } else { puts
"You set wrong data" }
Result:Your level is A
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switchswitch ?option? string pattern body ?pattern body. switch
?option? string {pattern body ?pattern body}
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(switch)Ex.:set num 1 switch $num { 1 {puts "Im 2 {puts "Im 3
{puts "Im default {puts } David."} Terry."} Ruby."} "Whats your
name?"}
Result:Im David.
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While Loop while booleanExpr body
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(while loop)1+2++100Ex.: set a 0 set ans 0 while {$a < 101} {
set ans [expr $ans+$a] incr a 1 } puts $ans Result: 5050Tango
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Foreach loop foreach loopVar valueList commandBody
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(foreach loop)1+2++10Ex.: Set j 0 foreach i {1 2 3 4 5 6 7 8 9
10} { set j [expr $i+$j] } puts $j Result: 55
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For loop for initial test final body
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(for loop)1+2++100Ex.: set ans 0 for {set a 0} {$a < 101}
{incr a 1} { set ans [expr $ans+$a] } puts $ans Result: 5050
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!
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Tcl(Tcl procedures)proc {1 2} { Body }
Procedures behave just like built-in commands:sub1 3 => 2
Arguments can have default values:proc decr {x {y 1}} { expr
$x-$y }Tango Training 54
procedures can be created dynamicallyproc power {base p} { set
result 1 while {$p > 0} { set result [expr $result * $base] set
p [expr $p-1] } return $result }
power 2 6
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Regular expressionsTclregexp regsub egrep ^$.+?\>\returns 1
regexp T(cl|k) "I mention Tk" w t => returns 1 (match), w
becomes "Tk", t gets "k"Tango Training 57
. (period) ^ $ \x [chars] (regexp) * + ? | matches any character
matches start of a string matches end of a string single character
escape matches any of chars. ^: not. -: range. matches the regexp
matches 0 or more of the preceding matches 1 or more of the
preceding matches 0 or 1 of the preceding can be used to divide
alternatives.Tango Training 58
catch catch,TCL_OK, 10 Can intercept errors (like exception
handling):catch {expr {2 +}} msg 1 (catch returns 0=OK, 1=err,
other values...) puts msg syntax error in expression "2 +"....
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(File I/O)Tcl file I/O commands:open close fblocked eof gets
seek flush read tell cd fileevent puts pwd filename glob fconfigure
source
File commands use 'tokens' to refer to files set f [open
"myfile.txt" "r"] => file1 () puts $f "Write this text into
file" close $fTango Training 60
gets and puts are line oriented set x [gets $f] reads one line
of $f into x set f [open /etc/passwd r] => file2 () gets $f
=> root:x:0:0:root:/root:/bin/bash
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read can read specific numbers of bytes read $f 100 => (up to
100 bytes of file $f) seek, tell, and read can do random-access I/O
set f [open "database" "r"] seek $f 1024 read $f 100 => (bytes
1024-1123 of file $f)
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infowhat variables are there?info vars, info globals, info
locals, info exists
what procedures have I defined, and how?info procs, info args,
info default, info body, info commands
proc ff {abc} {puts Hello} info args ff =>abc
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