Purpose: to describe awk, an early [Unix] [tiny language] named after the initials of its authors, Aho, Weinberger, Kernighan.

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See http://cm.bell-labs.com/cm/cs/awkbook/index.html
which is a page for an ''official'' book by the creators of the language.
See also the [usenet] newsgroup news:comp.lang.awk .
Another good resource for awk documentation is
http://www.gnu.org/software/gawk/manual/gawk.html .

http://www.vectorsite.net/tsawk.html is a comprehensive intro to awk, suitable to beginners. There are a number of other sites offering tutorials and introductions.

Programmers often come to the Tcl newsgroups asking [how can I do this awk like operation in Tcl] 
or how to invoke awk from exec.  
This is because Awk's ability to scan through a file and manipulate the contents 
pre-dates [Perl]'s functionality to do this, and frankly awk's abilities, 
while cruder in many ways, are also simpler (simpler even than Tcl!).

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The [BOOK Mastering Regular Expressions] covers [regular expressions] in [perl], awk, and [tcl].
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[LV] awk is one of my favorite languages in which to write...

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For a Tcl variation on awk functionality, see [owh - a fileless tclsh].

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[LV] A common question is:

How can I invoke awk scripts from Tcl?
 $ tclsh 
 % set a [exec awk {'{print $1}'} /etc/motd]
 awk: cmd. line:1: '{print $1}'
 awk: cmd. line:1: ^ invalid char ''' in expression

[RS] answers: This is not an awk problem, but a misuse of /bin/sh et al. quoting: 
single quotes there have the effect as braces in Tcl - group in one word, don't substitute on contents. Solution here: You have outer braces already, so just drop the single quotes (the inner brace pair is awk syntax, not seen by Tcl):
 % set a [exec awk {{print $1}} /etc/motd]
 
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[RS] 2007-02-07: I love this few-liner that allows tests in a subset of awk notation (in fact, the common subset of awk and [expr], plus a shortcut for [regexp]):
 proc awktest {filter 0} {
    if {[regexp {^/(.+)/$} $filter -> re]} {return [regexp $re $0]}
    set i 0
    foreach field $0 {set [incr i] $field}
    expr $filter
 }
e.g.:
 awktest {$1==$2} {foo bar grill} ->  0.
The variable $0 just is the input list :^) The following shortcut is also cute:
 interp alias {} ~ {} regexp
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[RS] 2007-11-08: When porting awk scripts, it's also helpful to have the numbered variables:
 proc awksplit {list sep} {
    set i 0
    foreach field [split $list $sep] {uplevel 1 [list set [incr i] $field]}
    upvar 1 [list set NF $i]
 }
where for example ''awksplit "foo;bar;grill" ";"'' assigns foo to 1, bar to 2, grill to 3.
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[RS] 2007-02-28: Here's another piece of awk emulation:
 proc substr {str from length} {
   string range $str [expr {$from-1}] [expr {$from-2+$length}]
 }
 % substr hello 2 2
 el
 % substr hello 2 99
 ello
And this is trivial, but over 50% shorter to type:
 interp alias {} length {} string length

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[Category Language] - [Category String Processing]