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;;; shell.scm -- Remote shell.
;; Copyright (C) 2016, 2017, 2020 Artyom V. Poptsov <poptsov.artyom@gmail.com>
;;
;; This file is a part of Guile-SSH.
;;
;; Guile-SSH 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.
;;
;; Guile-SSH 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 Guile-SSH. If not, see
;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;; Remote shell.
;;
;; The module provides the following procedures:
;; rexec
;; which
;; pgrep
;; pkill
;; command-available?
;; loadavg
;;
;; See the Info documentation for detailed description of these exceptions and
;; aforementioned procedures.
;;; Code:
(define-module (ssh shell)
#:use-module (srfi srfi-11)
#:use-module (ice-9 rdelim)
#:use-module (ice-9 regex)
#:use-module (ice-9 format)
#:use-module (ice-9 receive)
#:use-module (ice-9 ftw)
#:use-module (srfi srfi-1)
#:use-module (ssh channel)
#:use-module (ssh popen)
#:use-module (ssh dist node)
#:use-module (ssh log)
#:export (rexec
which
pgrep
pkill
command-available?
guile-version
loadavg))
(define (rexec session cmd)
"Execute a command CMD on the remote side. Return two values: list of
output lines returned by CMD and its exit code."
(let* ((channel (open-remote-input-pipe session cmd))
(result (let loop ((line (read-line channel))
(result '()))
(if (eof-object? line)
(reverse result)
(loop (read-line channel)
(cons line result)))))
(exit-status (channel-get-exit-status channel)))
(close channel)
(values result exit-status)))
(define (which session program-name)
"Check if a PROGRAM-NAME is available on a remote side. Return two values:
a check result and a return code."
(rexec session (format #f "which '~a'" program-name)))
(define* (%guile-pgrep session pattern #:key (full? #f))
(node-eval
(make-node session)
`(begin
(use-modules (ice-9 ftw)
(ice-9 rdelim)
(ice-9 format)
(ice-9 regex)
(srfi srfi-1))
(let ((procs (scandir "/proc" (lambda (e) (string-match "^[0-9]+" e)))))
(fold (lambda (entry prev)
(let* ((cmdline-file (format #f "/proc/~a/status" entry))
(cmdline-port (open-input-file cmdline-file)))
(if cmdline-port
(let ((cmdline (read-line cmdline-port)))
(cond
((eof-object? cmdline)
prev)
((and ,full? (string=? ,pattern cmdline))
(cons (string->number entry) prev))
((string-match ,pattern cmdline)
(cons (string->number entry) prev))
(else
prev)))
prev)))
(quote ())
procs)))))
(define* (%guile-pkill session pattern
#:key
(full? #f)
(signal SIGTERM))
"Guile-SSH implementation of 'pkill' that uses Guile on the remote side.
Note that this procedure won't work if Guile is missing on a target machine.
Send a SIGNAL to a process which name matches to PATTERN on a remote machine
represented by a SESSION. Return two values: a pkill result and a return
code."
(let ((pids (%guile-pgrep session pattern #:full? full?)))
(format-log 'functions
"[SCM] %guile-pkill"
"pids: ~a"
pids)
(node-eval
(make-node session)
`(begin
(for-each (lambda (pid) (kill pid ,signal))
(quote ,pids))
(quote ,pids)))))
;; We should use short '-f' option for pgrep and pkill instead of the long
;; version of it ('--full') because the long version was added on september
;; 2011 (according to the commit log of procps-ng [1]) and some systems may
;; not support it due to older procps.
;;
;; [1] https://gitlab.com/procps-ng/procps/commit/4581ac2240d3c2108c6a65ba2d19599195b512bc
(define* (pgrep session pattern
#:key
(full? #f)
(use-guile? #f))
"Check if a process with a PATTERN cmdline is available on a machine
represented by a SESSION. Return two values: a check result and a return
code."
(if use-guile?
(receive (result eval-number module-name lang-name)
(%guile-pgrep session pattern #:full? full?)
(values result 0))
(receive (result exit-code)
(rexec session (format #f
"pgrep ~a '~a'"
(if full? "-f" "")
pattern))
(values (map string->number result) exit-code))))
(define* (pkill session pattern #:key
(full? #f)
(signal SIGTERM)
(use-guile? #f))
"Send a SIGNAL to a process which name matches to PATTERN on a remote
machine represented by a SESSION. Return two values: a pkill result and a
return code."
(if use-guile?
(receive (result eval-number module-name lang-name)
(%guile-pkill session pattern #:full? full? #:signal signal)
(values result 0))
(rexec session (format #f "pkill ~a --signal ~a '~a'"
(if full? "-f" "")
signal
pattern))))
(define (command-available? session command)
"check if COMMAND is available on a remote side."
(receive (result rc)
(which session command)
(zero? rc)))
(define (procps-available? session)
"Check if procps is available on a NODE."
(command-available? session "pgrep"))
(define (guile-version session)
"Get Guile version installed on a remote side, return the version string.
Return #f if Guile is not installed."
(receive (result rc)
(rexec session "which guile > /dev/null && guile --version")
(and (zero? rc)
(car result))))
(define (loadavg session)
"Get average load of a host using a SESSION."
(receive (result exit-status)
(rexec session "cat /proc/loadavg")
(unless (zero? exit-status)
(throw 'guile-ssh-error "Could not get average load for a host" session))
(string-split (car result) #\space)))
;;; shell.scm ends here.
|
