Tcl Language Cheat Sheet

List operations

lappend <list> $ele	$ele is added to list as a single index
set A1 [concat $list1 "ABC" $list2 $var2]; #concat will add lists as a separate indexes, if list 1 contains 3 elements it will add 3 index values; ○ If you want to maintain list structure use lappend, if you want simple list with all the elements separate use concat
llength <$list>	length of a list
lindex <$list> <#index_no> ?<#2nd index_no in case of nested list>?
lrange <$list> <#1st_index> <#2nd_index>; #Returns elements from 1st index to 2nd index
linsert <$var> <#index_position> <ele1> <ele2> <ele3> .... ; #Output: will have list added at index position
linsert <$list> <#index_position> <ele1> <ele2> <ele3> .... ; # Output will have separate elements, first index will be WHOLE original list
lreplace <$list> <#start_index> <#end_index> <item1> <item2> <item3>...; # replace items between start and end indexes with item1, item2 .....
lsearch ?-<all\| dictionary\| decreasing\| glob\| exact\| regexp\| not\| sorted\| integer\| real\| #start_index>? <$list> <pattern>
lsort ?-<ascii\| dictionary\| integer\| real\| increasing\| decreasing\| #index_sublist\| unique>? <$list> # index option =3 will sort the main list based on 4th element of each sublist
split <$list/$var> ?<chars>?	String to list
join <$list/$var> ?<chars>?	List to string

○ set random [list a b c {bad} { had } 123 1a2b "1.22" 15.43 $had $tag {A B C D E F G}]; #Here each element is a separate element, each list with grouping is a single element
○ list $a $b $c; #Here list contains 3 elements only, even though a b or c contains list inside it

String operations

string match ?-nocase? <pattern> <string> # if pattern matches string output is 1

string equal ?-nocase|-length int? <string1> <string2> # Returns 1 if string1 and string2 are identical, or 0 when not.

string compare ?-nocase|-length #N? <string1> <string2> #check strings lexicographically, if string1> string2 output is 1

string map {<from> <to>} <string> #string map {H 000} $a 17 #replace H in Hello with 000

string replace <string> <#start_index> <#end_index> ?<replacement_string>?

subst ?-nobackslashes? ?-nocommands? ?-novariables? string #set a 44 ;subst {xyz {$a}}; output is xyz{44}

string range <string> <#start_index> <#end_index>

puts [format "Today is %s %d %f" $day $month $year]

string length <string>

string first <char or pattern to search> <string> ?<start index>?

string index <string> <index #| end|end-n>

string bytelength <string>

string last <char or pattern to search> <string> ?<end index>?

string repeat <string> <#count>

string toupper/tolower/totitle <string> ?<#start_index>? ?<#end_index>?

string trimleft/trimright/trim <string> ?<chars>?

append <string_var> $x, $y # "ZZZ"

string reverse <string>

string wordend|wordstart <string> <#index>

Arrays

array set array1 [list {123} {Abigail Aardvark} \ 		       {234} {Bob Baboon} \                        {345} {Cathy Coyote} \ 		       {456} {Daniel Dog} ]

set fruit(Apple) 143

array size <arrayname> ; #

array names <arrayname> ?<pattern>?;# gives all the keys as iteratable list

array get <arrayname>; # returns list where each odd member is key and even is value

array exists <arrayname>

foreach key [array names array1] {   puts "Key is $key and value is $array1($key)";   }

parray <arrayname>; #

array startsearch <arrayName>; #

array nextelement <arrayName> <searchID> ;#

array anymore <arrayName> <searchID>

array donesearch <arrayName> <searchID>

Dictionaries

dict set <DICT NAME><Key1> <value1> #create a dict with DICT_NAME key and value

dict set <DICT NAME><Key1> <nested Key1_1> <value1> #create a dict with DICT_NAME key and value

set <DICT NAME> [dict create 1 "SK" 2 "KK" 3 "ZK"] #1 is key and SK in value

dict unset names <$DICT_NAME> ; #removes key/value pair

dict replace <$DICT NAME> <key> <new_value> ;#replace the value corresponding to key

dict keys <$DICT_NAME> ; #provides all the keys as list

dict values <$DICT_NAME>; #provides all values as list

dict get $<DICT_NAME> <key> ;#returns value on that key:ZK

dict get $DICT_NAME ;#returns all key and value pair as a list

dict for {key value} $DICT { puts "Key:$key Value:$value";}

foreach keys [dict keys $DICT] { puts "Key:$keys Values [dict get $DICT $keys]"; }

dict append <DICT_NAME> 4 LA;#adds one key to dictionary

dict lappend <DICT_NAME> 4 LA SF PO;#adds values as a single value to key 4

set filtered [dict filter $<DICT_NAME> key|value|script 1] ;#filter by name value or script

set filtered [dict filter $<DICT_NAME> script {key value} {Expr {$key < 3 }}] ;# returns 1 SK 2 KK

dict exists $names <key> ;# Checks for key 3 in names dict, returns 1 is key exists

dict incr $names one<key> 4<increment by> ;#increments value by integer <value>

dict info $names ; # provides info on dict

set merged [dict merge $test1 $test2] ; #merges two dicts

set new [dict remove $test <key1> <key2> ....] ; # removes key/value pair based on specif ied keys

#### Dictionary modification

dict size $names ; #get the number of key/value pairs

# Define a simple dict: {a b c d} ; set dd [dict create a b c d] ; dict update dd a aVar c cVar {     set aVar 2;      set cVar [string toupper $cVar];  } # displays {a 2 c D} set dd

Dictionary Examples

dict for {key value} $names {
        puts "Key is: $key and Value is: $value"
        }
foreach key [dict keys $name_number_dict] value [dict values $name_number_dict] { 
              puts "$key == $value"
              }

#dict update
        % set didi {key1 value1 key2 value2}
        key1 value1 key2 value2
        % dict update didi key1 varKey1 key2 varKey2 {
            append varKey1 new
            append varKey2 new
            unset varKey1; #deletes key value pair
          }
        value2new
        % set didi
        key1 value1new key2 value2new
#dict with : you can convert key names to variables directly
        % set pers_detail [dict create forenames Joe surname Schmoe street {147 Short Street} \
            city Springfield phone 555-1234]
        dict with pers_detail {
            puts "   Name: $forenames $surname"
            puts "   Address: $street, $city"
            puts "   Telephone: $phone"
        }


**##Inventory system
KEY    FIRST    LAST      TITLE
1      Clif     Flynt     Tcl/Tk For Real Programmers
2      Clif     Flynt     Tcl/Tk: A Developer's Guide 2'nd edition
3      Brent    Welch     Practical Programming in Tcl/Tk
4      Michael  McClennan Effective Tcl/Tk Programming
5      Don      Libes     Exploring Expect

dict set books 1 [list first Cliff last Flint title "Tcl/TK a dev guide" year 2009]

dict set books 2 first Brent 
dict set books 2 last Welch
dict set books 2 title "Practical Programming in Tcl/Tk"
dict set books 2 year 1867

foreach {sr first last title year} {
    	3      Michael  McClennan {Effective Tcl/Tk Programming} 2001
    	4      Don      Libes     {Exploring Expect} 2008 } {
    	dict set books $sr [list first $first last $last title $title year $year]
    	}
#set first firsttest
dict for {sr infor} $books {
	dict with infor {
		puts "$sr $first $last $title $year"
		}
	}**

Looping

while {<test exp>} { <body> }

for {set i 10} {$i>=0} {incr i-1} { <body> }

foreach ele $list { <body> }

foreach {ele1 ele2} $list { <body> }; # 2 elements are taken from list2 for each iteration

foreach ele1 $list1 ele2 $list2 { <body> }; # l1 iterates over list1 and l2 iterates over list2

Switch

	• switch ?-option (exact, glob, regexp, nocase) --? $string \
		$pattern_1 {body} \
		$pattern_2 {body} \
		.
		.
		default {body}; 
		
	• switch ?-option (exact, glob, regexp, nocase) --? $string \
		{A body}
		{B body}
		.
		.
		{default body};
		Here pattern substitutions cannot occur

procs

	• Proc with optional arguments
		proc random_num {min {max 100}} {
						<body>
						}
	• Proc with variable number of arguments
		proc random_num {args} {
						puts $args; llength $args; lindex $args 0;
						<body>
						}

regex

regexp ? <about| expanded| indices| line| linestop| lineanchor| nocase| all| inline| start| #index_start>? {<regex_to_match>} <$string> match submatch1 submatch2 .....

regsub ? <all| expanded| line| linestop| lineanchor| nocase| inline| #index_start>? {<regex_to_match>} <$string> {<regex_to_replace>} ?<storage_variable>?

Regsub
○ \1: 1st grouping match
○ \2: 2nd grouping match
○ &: whole expression/inside {} match
○ command returns replaced string dictated by regex to replace {}
○ if storage_variable specified, return 1 or 0 depending on <regex to match> or not
○

regsub {(\w+).(\w+)} "report.txt" {\1.tcl} ext

puts $ext (output will be report.tcl)

File IO

set FILEHANDLE [ open <filename> ?access_mode (r| r+| w| w+| a | a+)? ?permissions(755, 744, 777)?

close $FILEHANDLE

if {[catch {set FILEHANDLE [ open <filename> r+] } ?<error_var>?]} { puts $error_var; <body> }

r+ mode does not create a file if it does not exists, where a+/w+ will create a file if it does not exist

Reading a file proc (memory)

proc read_file_less_memory {file_in} {
        if {[file exists $file_in]} {
                set fh [open $file_in r]; 
                while {[gets $fh line] >= 0} {
                        lappend file_data $line;
                }   
                close $fh;
                return $file_data;
        } else {
                puts "File does not exist."
}

Reading a file proc

proc read_file {f} {
               puts "Reading :\t $f";
               if {[catch {set fh [open $f r]} err] } {
                  puts "File does not exist $f:$err";
                  } else {
                        set fh [open $f r];
                        set fdata [split [read $fh] "\n"]
                        close $fh;
                        return $fdata;
                  }
         }

MISC

User input	gets stdin <VAR NAME TO ASSIGN VALUE>
Random number	set i [expr {int(rand() * 6)}]
global	change the scope of the variables to global from inside proc
Upvar	Used to pass by value to a proc, while instantiating proc do not provide values with a $sign, leave out $sign ; `
argc	number of command line arguments
argv0	Script name
argv	all command line arguments
set A1 [lindex $argv 0]	first argument

Error Handling

Error Handling:

proc Div {a b} {
   if {$b == 0} {
      error "Error generated by error" "Info String for error" 401
       error <Error Message> <Error Info> <Error code>
   } else {
      return [expr $a/$b]
   }
}

if {[catch {puts "Result = [Div 10 0]"} errmsg]} {
   puts "ErrorMsg: $errmsg"
   puts "ErrorCode: $errorCode"
   puts "ErrorInfo:\n$errorInfo\n"
}

Upper/Global

Global/By value:

proc by_global {A B C} {
        global j1; 
        global j2; 
        global j3; 

        set j1 $A; set j2 $B; set j3 $C; 
        puts "In $j1 $j2 $j3"
}

by_global 100 200 300 

Upvar/By reference:
proc by_reference {P Q R} {

        upvar $P p;
        upvar $Q q;
        upvar $R r;
        set p [expr $p*2];
        set q [expr $q*2];
        set r [expr $r*2];

        puts "Inside upvar: $p $q $r";

}


by_reference j1 j2 j3;

To Do

Multi- Dimensional Arrays

How to set command line arguments for a scripts?

packages vs module vs namespace vs proc

namespace

parse_proc_arguments

seek/tell

upvar

uplevel

lset

string map

How to set up Help for a script?

$argv and $argc

global

Scan

Current Time & Date

set systemTime [clock seconds]
set current_time [clock format $systemTime -format %H:%M:%S]
set ct [clock format $systemTime -format %H_%M]
set current_date [clock format $systemTime -format %D]
set cdt [clock format $systemTime -format %m_%d_%y]

Tcl Language Cheat Sheet (DRAFT) by AHA

List operations

String operations

Arrays

Dictionaries

Dictionary Examples

Looping

Switch

procs

regex

File IO

Reading a file proc (memory)

Reading a file proc

MISC

Error Handling

Upper/Global

To Do

Current Time & Date

Latest Cheat Sheet

Random Cheat Sheet

About Cheatography

Behind the Scenes

Recent Cheat Sheet Activity

Please Disable Your Ad Blocker

Tcl Language Cheat Sheet (DRAFT) by AHA

List operations

String operations

Arrays

Dictio­naries

Dictionary Examples

Looping

Switch

procs

regex

File IO

Reading a file proc (memory)

Reading a file proc

MISC

Error Handling

Upper/­Global

To Do

Current Time & Date

Latest Cheat Sheet

Random Cheat Sheet

About Cheatography

Behind the Scenes

Recent Cheat Sheet Activity

Please Disable Your Ad Blocker

Dictionaries

Upper/Global