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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix 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 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix 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 GNU Guix. If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix scripts processes)
+ #:use-module ((guix store) #:select (%store-prefix))
+ #:use-module (guix scripts)
+ #:use-module (guix ui)
+ #:use-module (srfi srfi-1)
+ #:use-module (srfi srfi-9)
+ #:use-module (srfi srfi-9 gnu)
+ #:use-module (srfi srfi-37)
+ #:use-module (ice-9 ftw)
+ #:use-module (ice-9 match)
+ #:use-module (ice-9 rdelim)
+ #:use-module (ice-9 format)
+ #:export (process?
+ process-id
+ process-parent-id
+ process-command
+ processes
+
+ daemon-session?
+ daemon-session-process
+ daemon-session-client
+ daemon-session-children
+ daemon-session-locks-held
+ daemon-sessions
+
+ guix-processes))
+
+;; Process as can be found in /proc on GNU/Linux.
+(define-record-type <process>
+ (process id parent command)
+ process?
+ (id process-id) ;integer
+ (parent process-parent-id) ;integer | #f
+ (command process-command)) ;list of strings
+
+(define (write-process process port)
+ (format port "#<process ~a>" (process-id process)))
+
+(set-record-type-printer! <process> write-process)
+
+(define (read-status-ppid port)
+ "Read the PPID from PORT, an input port on a /proc/PID/status file. Return
+#f for PID 1 and kernel pseudo-processes."
+ (let loop ()
+ (match (read-line port)
+ ((? eof-object?) #f)
+ (line
+ (if (string-prefix? "PPid:" line)
+ (string->number (string-trim-both (string-drop line 5)))
+ (loop))))))
+
+(define %not-nul
+ (char-set-complement (char-set #\nul)))
+
+(define (read-command-line port)
+ "Read the zero-split command line from PORT, a /proc/PID/cmdline file, and
+return it as a list."
+ (string-tokenize (read-string port) %not-nul))
+
+(define (processes)
+ "Return a list of process records representing the currently alive
+processes."
+ ;; This assumes a Linux-compatible /proc file system. There exists one for
+ ;; GNU/Hurd.
+ (filter-map (lambda (pid)
+ ;; There's a TOCTTOU race here. If we get ENOENT, simply
+ ;; ignore PID.
+ (catch 'system-error
+ (lambda ()
+ (define ppid
+ (call-with-input-file (string-append "/proc/" pid "/status")
+ read-status-ppid))
+ (define command
+ (call-with-input-file (string-append "/proc/" pid "/cmdline")
+ read-command-line))
+ (process (string->number pid) ppid command))
+ (lambda args
+ (if (= ENOENT (system-error-errno args))
+ #f
+ (apply throw args)))))
+ (scandir "/proc" string->number)))
+
+(define (process-open-files process)
+ "Return the list of files currently open by PROCESS."
+ (let ((directory (string-append "/proc/"
+ (number->string (process-id process))
+ "/fd")))
+ (map (lambda (fd)
+ (readlink (string-append directory "/" fd)))
+ (or (scandir directory string->number) '()))))
+
+;; Daemon session.
+(define-record-type <daemon-session>
+ (daemon-session process client children locks)
+ daemon-session?
+ (process daemon-session-process) ;<process>
+ (client daemon-session-client) ;<process>
+ (children daemon-session-children) ;list of <process>
+ (locks daemon-session-locks-held)) ;list of strings
+
+(define (daemon-sessions)
+ "Return two values: the list of <daemon-session> denoting the currently
+active sessions, and the master 'guix-daemon' process."
+ (define (lock-file? file)
+ (and (string-prefix? (%store-prefix) file)
+ (string-suffix? ".lock" file)))
+
+ (let* ((processes (processes))
+ (daemons (filter (lambda (process)
+ (match (process-command process)
+ ((argv0 _ ...)
+ (string=? (basename argv0) "guix-daemon"))
+ (_ #f)))
+ processes))
+ (children (filter (lambda (process)
+ (match (process-command process)
+ ((argv0 (= string->number argv1) _ ...)
+ (integer? argv1))
+ (_ #f)))
+ daemons))
+ (master (remove (lambda (process)
+ (memq process children))
+ daemons)))
+ (define (lookup-process pid)
+ (find (lambda (process)
+ (and (process-id process)
+ (= pid (process-id process))))
+ processes))
+
+ (define (lookup-children pid)
+ (filter (lambda (process)
+ (and (process-parent-id process)
+ (= pid (process-parent-id process))))
+ processes))
+
+ (values (map (lambda (process)
+ (match (process-command process)
+ ((argv0 (= string->number client) _ ...)
+ (let ((files (process-open-files process)))
+ (daemon-session process
+ (lookup-process client)
+ (lookup-children (process-id process))
+ (filter lock-file? files))))))
+ children)
+ master)))
+
+(define (daemon-session->recutils session port)
+ "Display SESSION information in recutils format on PORT."
+ (format port "SessionPID: ~a~%"
+ (process-id (daemon-session-process session)))
+ (format port "ClientPID: ~a~%"
+ (process-id (daemon-session-client session)))
+ (format port "ClientCommand:~{ ~a~}~%"
+ (process-command (daemon-session-client session)))
+ (for-each (lambda (lock)
+ (format port "LockHeld: ~a~%" lock))
+ (daemon-session-locks-held session))
+ (for-each (lambda (process)
+ (format port "ChildProcess: ~a:~{ ~a~}~%"
+ (process-id process)
+ (process-command process)))
+ (daemon-session-children session)))
+
+
+;;;
+;;; Options.
+;;;
+
+(define %options
+ (list (option '(#\h "help") #f #f
+ (lambda args
+ (show-help)
+ (exit 0)))
+ (option '(#\V "version") #f #f
+ (lambda args
+ (show-version-and-exit "guix processes")))))
+
+(define (show-help)
+ (display (G_ "Usage: guix processes
+List the current Guix sessions and their processes."))
+ (newline)
+ (display (G_ "
+ -h, --help display this help and exit"))
+ (display (G_ "
+ -V, --version display version information and exit"))
+ (newline)
+ (show-bug-report-information))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-processes . args)
+ (define options
+ (args-fold* args %options
+ (lambda (opt name arg result)
+ (leave (G_ "~A: unrecognized option~%") name))
+ cons
+ '()))
+
+ (for-each (lambda (session)
+ (daemon-session->recutils session (current-output-port))
+ (newline))
+ (daemon-sessions)))
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