Tcl Cheat Sheet

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The Tool Command Language (Tcl) is the scripting language integrated in the Vivado ® tool environment. Tcl is a standard language in the semiconductor industry for application programming interfaces, and is used by Synopsys ® Design Constraints (SDC). SDC is the mechanism for communicating timing constraints for FPGA synthesis tools from. F5 Cheat Sheet Edit Cheat Sheet F5 irule Regex Examples. Note that F5 uses TCL as a scripting language, so all these commands do follow TCL syntax. Matching with regexp.

Tcl Regex Cheat Sheet

Modern combat 4 graphic patch. Tcl also supports string operations known as regularexpressions Several commands can access these methods with a-regexp argument, see the man pages for which commands supportregular expressions.

There are also two explicit commands for parsing regularexpressions.

regexp?switches?expstring?matchVar??subMatch1 .. subMatchN?
Searches string for the regularexpression exp. If a parameter matchVar is given, then the substring thatmatches the regular expression is copied to matchVar. If subMatchN variables exist, then theparenthetical parts of the matching string are copied to thesubMatch variables, working from leftto right.
regsub?switches?expstringsubSpecvarName
Searches string for substrings thatmatch the regular expression exp andreplaces them with subSpec. Theresulting string is copied into varName.

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Regular expressions can be expressed in just a few rules.

^
Matches the beginning of a string
$
Matches the end of a string
.
Matches any single character
*
Matches any count (0-n) of the previous character
+
Matches any count, but at least 1 of the previous character
[..]
Matches any character of a set of characters
[^..]
Matches any character *NOT* a member of the set of charactersfollowing the ^.
(..)
Groups a set of characters into a subSpec.

Tcl Cheat Sheet 2019

Regular expressions are similar to the globbing that wasdiscussed in lessons 16 and 18. The main difference is in theway that sets of matched characters are handled. In globbingthe only way to select sets of unknown text is the * symbol. This matches to any quantityof any character.

In regular expression parsing, the * symbol matches zero or more occurrencesof the character immediately proceeding the *. For example a* would match a, aaaaa, or a blankstring. If the character directly before the * is a set of characters within squarebrackets, then the * will match anyquantity of all of these characters. For example, [a-c]* would match aa, abc, aabcabc, oragain, an empty string.

The + symbol behaves roughly thesame as the *, except that itrequires at least one character to match. For example, [a-c]+ would match a, abc, or aabcabc,but not an empty string.

Regular expression parsing is more powerful than globbing. Withglobbing you can use square brackets to enclose a set ofcharacters any of which will be a match. Regular expressionparsing also includes a method of selecting any characternot in a set. If the first character after the [ is a caret (^), then the regular expression parserwill match any character not in the set of characters betweenthe square brackets. A caret can be included in the set ofcharacters to match (or not) by placing it in any position otherthan the first.

The regexp command is similar tothe string match command in that itmatches an exp against a string.It is different in that it can match a portion of a string,instead of the entire string, and will place the charactersmatched into the matchVar variable.

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If a match is found to the portion of a regularexpression enclosed within parentheses, regexp will copy the subset of matchingcharacters is to the subSpecargument. This can be used to parse simple strings.

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Regsub will copy the contents ofthe string to a new variable, substituting the characters thatmatch exp with the characters insubSpec. If subSpec contains a & or 0,then those characters will be replaced by the characters thatmatched exp. If the number following abackslash is 1-9, then that backslash sequence will be replacedby the appropriate portion of exp thatis enclosed within parentheses.

Note that the exp argument to regexp or regsub is processed by the Tclsubstitution pass. Therefore quite often the expression isenclosed in braces to prevent any special processing by Tcl.

Example

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The 'regexp' command is used to match a regular expression in Tcl. A regular expression is a sequence of characters that contains a search pattern. It consists of multiple rules and the following table explains these rules and corresponding use.

Sr.No.Rule & Description
1

x

Exact match.

2

[a-z]

Any lowercase letter from a-z.

3

.

Any character.

4

^

Beginning string should match.

5

$

Ending string should match.

6

^

Backlash sequence to match special character ^.Similarly you can use for other characters.

7

()

Add the above sequences inside parenthesis to make a regular expression.

8

x*

Should match 0 or more occurrences of the preceding x.

9

x+

Should match 1 or more occurrences of the preceding x.

10

[a-z]?

Should match 0 or 1 occurrence of the preceding x.

11

{digit}

Matches exactly digit occurrences of previous regex expression. Digit that contains 0-9.

12

{digit,}

Matches 3 or more digit occurrences of previous regex expression. Digit that contains 0-9.

13

{digit1,digit2}

Occurrences matches the range between digit1 and digit2 occurrences of previous regex expression.

Syntax

The syntax for regex is given below −

Here, regex is the command. We will see about optional switches later. Patterns are the rules as mentioned earlier. Search string is the actual string on which the regex is performed. Full match is any variable to hold the result of matched regex result. Submatch1 to SubMatchn are optional subMatch variable that holds the result of sub match patterns.

Let's look at some simple examples before diving into complex ones. A simple example for a string with any alphabets. When any other character is encountered the regex, search will be stopped and returned.

Tcl Cheat Sheet 2020

When the above code is executed, it produces the following result −

Multiple Patterns

The following example shows how to search for multiple patterns. This is example pattern for any alphabets followed by any character followed by any alphabets.

When the above code is executed, it produces the following result −

A modified version of the above code to show that a sub pattern can contain multiple patterns is shown below −

When the above code is executed, it produces the following result −

Switches for Regex Command

The list of switches available in Tcl are, Black coffee buya zippy.

  • nocase − Used to ignore case.

  • indices − Store location of matched sub patterns instead of matched characters.

  • line − New line sensitive matching. Ignores the characters after newline.

  • start index − Sets the offset of start of search pattern.

  • Pes 13 repack. Marks the end of switches

In the above examples, I have deliberately used [A-Z, a-z] for all alphabets, you can easily use -nocase instead of as shown below −

When the above code is executed, it produces the following result −

Another example using switches is shown below −

When the above code is executed, it produces the following result −