1: #!/usr/bin/env gosh
    2: 
    3: (define (usage program-name)
    4:   (format (current-error-port)
    5:           "Usage: ~a regexp file ...\n" program-name)
    6:   (exit 2))
    7: 
    8: (define (grep rx)
    9:   (port-for-each
   10:    (lambda (line)
   11:      (when (rx line)
   12:        (format #t "~a:~a: ~a\n"
   13:                (port-name (current-input-port))
   14:                (- (port-current-line (current-input-port)) 1)
   15:                line)))
   16:    read-line))
   17: 
   18: (define (main args)
   19:   (when (null? (cdr args)) (usage (car args)))
   20:   (let1 rx (string->regexp (cadr args))
   21:     (if (null? (cddr args))
   22:         (grep rx)
   23:         (for-each (cut with-input-from-file <> (cut grep rx))
   24:                   (cddr args))))
   25:   0)
   26: