#!/usr/bin/env sh
# -*- scheme -*-
exec guile -L $(dirname $(dirname $(realpath "$0"))) -e '(@@ (examples pipe) main)' -s "$0" "$@"
; !#

;; Use pipes to connect several commands

(define-module (examples pipe)
    #:export (!))

(import (ice-9 popen)
         (ice-9 rdelim)
         (only (srfi srfi-1) fold)
         (ice-9 pretty-print))

(define (! . cmds)
       "A pipe-procedure: connect each of the CMDS with the next
in the list, the first with stdin and the last with stdout."
       (define (read-till-eof in-port)
           (read-delimited "" in-port))
       (define (connect B A)
           (let 
               ((in-port (if (port? A) A (open-input-pipe A)))
                 (out-port (open-input-output-pipe B)))
               (pretty-print (cons A B))
               (let ((data (read-till-eof in-port)))
                 (pretty-print data)
                 (display data out-port))
               (close in-port)
               out-port))
       (fold connect (car cmds) (cdr cmds)))

(define (main args)
    (display (read-delimited "" (! "echo 1" "echo 2" "echo 3" "echo 4"))))