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;; popen emulation, for non-stdio based ports.
;;;; Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
;;;;
;;;; This program is free software; you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation; either version 2, or (at your option)
;;;; any later version.
;;;;
;;;; This program is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;;; GNU General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU General Public License
;;;; along with this software; see the file COPYING. If not, write to
;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
;;;; Boston, MA 02111-1307 USA
;;;;
;;;; As a special exception, the Free Software Foundation gives permission
;;;; for additional uses of the text contained in its release of GUILE.
;;;;
;;;; The exception is that, if you link the GUILE library with other files
;;;; to produce an executable, this does not by itself cause the
;;;; resulting executable to be covered by the GNU General Public License.
;;;; Your use of that executable is in no way restricted on account of
;;;; linking the GUILE library code into it.
;;;;
;;;; This exception does not however invalidate any other reasons why
;;;; the executable file might be covered by the GNU General Public License.
;;;;
;;;; This exception applies only to the code released by the
;;;; Free Software Foundation under the name GUILE. If you copy
;;;; code from other Free Software Foundation releases into a copy of
;;;; GUILE, as the General Public License permits, the exception does
;;;; not apply to the code that you add in this way. To avoid misleading
;;;; anyone as to the status of such modified files, you must delete
;;;; this exception notice from them.
;;;;
;;;; If you write modifications of your own for GUILE, it is your choice
;;;; whether to permit this exception to apply to your modifications.
;;;; If you do not wish that, delete this exception notice.
;;;;
(define-module (ice-9 popen)
:export (port/pid-table open-pipe close-pipe open-input-pipe
open-output-pipe))
;; (define-module (guile popen)
;; :use-module (guile posix))
;; a guardian to ensure the cleanup is done correctly when
;; an open pipe is gc'd or a close-port is used.
(define pipe-guardian (make-guardian))
;; a weak hash-table to store the process ids.
(define port/pid-table (make-weak-key-hash-table 31))
(define (ensure-fdes port mode)
(or (false-if-exception (fileno port))
(open-fdes *null-device* mode)))
;; run a process connected to an input or output port.
;; mode: OPEN_READ or OPEN_WRITE.
;; returns port/pid pair.
(define (open-process mode prog . args)
(let ((p (pipe))
(reading (string=? mode OPEN_READ)))
(setvbuf (cdr p) _IONBF)
(let ((pid (primitive-fork)))
(cond ((= pid 0)
;; child
(set-batch-mode?! #t)
;; select the three file descriptors to be used as
;; standard descriptors 0, 1, 2 for the new process. one
;; is the pipe to the parent, the other two are taken
;; from the current Scheme input/output/error ports if
;; possible.
(let ((input-fdes (if reading
(ensure-fdes (current-input-port)
O_RDONLY)
(fileno (car p))))
(output-fdes (if reading
(fileno (cdr p))
(ensure-fdes (current-output-port)
O_WRONLY)))
(error-fdes (ensure-fdes (current-error-port)
O_WRONLY)))
;; close all file descriptors in ports inherited from
;; the parent except for the three selected above.
;; this is to avoid causing problems for other pipes in
;; the parent.
;; use low-level system calls, not close-port or the
;; scsh routines, to avoid side-effects such as
;; flushing port buffers or evicting ports.
(port-for-each (lambda (pt-entry)
(false-if-exception
(let ((pt-fileno (fileno pt-entry)))
(if (not (or (= pt-fileno input-fdes)
(= pt-fileno output-fdes)
(= pt-fileno error-fdes)))
(close-fdes pt-fileno))))))
;; copy the three selected descriptors to the standard
;; descriptors 0, 1, 2. note that it's possible that
;; output-fdes or input-fdes is equal to error-fdes.
(cond ((not (= input-fdes 0))
(if (= output-fdes 0)
(set! output-fdes (dup->fdes 0)))
(if (= error-fdes 0)
(set! error-fdes (dup->fdes 0)))
(dup2 input-fdes 0)))
(cond ((not (= output-fdes 1))
(if (= error-fdes 1)
(set! error-fdes (dup->fdes 1)))
(dup2 output-fdes 1)))
(dup2 error-fdes 2)
(apply execlp prog prog args)))
(else
;; parent
(if reading
(close-port (cdr p))
(close-port (car p)))
(cons (if reading
(car p)
(cdr p))
pid))))))
(define (open-pipe command mode)
"Executes the shell command @var{command} (a string) in a subprocess.
A pipe to the process is created and returned. @var{modes} specifies
whether an input or output pipe to the process is created: it should
be the value of @code{OPEN_READ} or @code{OPEN_WRITE}."
(let* ((port/pid (open-process mode "/bin/sh" "-c" command))
(port (car port/pid)))
(pipe-guardian port)
(hashq-set! port/pid-table port (cdr port/pid))
port))
(define (fetch-pid port)
(let ((pid (hashq-ref port/pid-table port)))
(hashq-remove! port/pid-table port)
pid))
(define (close-process port/pid)
(close-port (car port/pid))
(cdr (waitpid (cdr port/pid))))
;; for the background cleanup handler: just clean up without reporting
;; errors. also avoids blocking the process: if the child isn't ready
;; to be collected, puts it back into the guardian's live list so it
;; can be tried again the next time the cleanup runs.
(define (close-process-quietly port/pid)
(catch 'system-error
(lambda ()
(close-port (car port/pid)))
(lambda args #f))
(catch 'system-error
(lambda ()
(let ((pid/status (waitpid (cdr port/pid) WNOHANG)))
(cond ((= (car pid/status) 0)
;; not ready for collection
(pipe-guardian (car port/pid))
(hashq-set! port/pid-table
(car port/pid) (cdr port/pid))))))
(lambda args #f)))
(define (close-pipe p)
"Closes the pipe created by @code{open-pipe}, then waits for the process
to terminate and returns its status value, @xref{Processes, waitpid}, for
information on how to interpret this value."
(let ((pid (fetch-pid p)))
(if (not pid)
(error "close-pipe: pipe not in table"))
(close-process (cons p pid))))
(define reap-pipes
(lambda ()
(let loop ((p (pipe-guardian)))
(cond (p
;; maybe removed already by close-pipe.
(let ((pid (fetch-pid p)))
(if pid
(close-process-quietly (cons p pid))))
(loop (pipe-guardian)))))))
(add-hook! after-gc-hook reap-pipes)
(define (open-input-pipe command)
"Equivalent to @code{open-pipe} with mode @code{OPEN_READ}"
(open-pipe command OPEN_READ))
(define (open-output-pipe command)
"Equivalent to @code{open-pipe} with mode @code{OPEN_WRITE}"
(open-pipe command OPEN_WRITE))
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