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awk

Description

A looping construct for processing input in a way similar to the awk tool.

Author

Originally by Olin Shivers. This implementation has been taken from PLT Scheme's awk library and minimally modified by felix winkelmann to work with CHICKEN.

Requirements

None

Documentation

See the SCSH documentation for awk.

Examples

Count non-comment lines in Scheme file:

(use awk)

(print
  (awk (read-line) (line) ([nlines 0])
    ("^[ \t]*;" nlines)
    (else (add1 nlines))))

Strip blank lines:

(use awk)

(awk (read-line) (line) ()
  ("[^ \t]" (print line)) )

Compute maximal line length:

(use awk)

(print 
  (awk (read-line) (line) ([max-len 0])
    (#t (max max-len (string-length line))))

Sort /etc/passwd file:

(use awk)

(define (read-passwd . port)
  (let ([line (apply read-line port)])
    (if (eof-object? line)
	(values line #f)
	(values line (string-split-fields ":" line #:infix)))))

(for-each
 (lambda (entry) (print (cdr entry)))
 (sort
  (awk (read-passwd) (line fields) ([ans '()])
    (#t (cons (cons (car fields) line) ans)) ) 
  (lambda (x y) (string<? (car x) (car y)))))

Changelog

License

 
 PLT Software
 Copyright (c) 1995-2002 PLT

 PLT software is distributed under the GNU Lesser General Public
 License (LGPL).