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;;; shell.scm -- Remote shell.
;; Copyright (C) 2016, 2017 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
;; fallback-pgrep
;; fallback-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 (ssh channel)
#:use-module (ssh popen)
#:use-module (ssh log)
#:export (rexec which pgrep pkill fallback-pgrep command-available?
fallback-pkill 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)))
;; 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))
"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."
(rexec session (format #f "pgrep ~a '~a'"
(if full? "-f" "")
pattern)))
(define* (pkill session pattern #:key (full? #f)
(signal 'SIGTERM))
"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."
(rexec session (format #f "pkill ~a --signal ~a '~a'"
(if full? "-f" "")
signal
pattern)))
(define* (fallback-pgrep session pattern #:key (full? #f))
"Guile-SSH implementation of 'pgrep' that uses pure bash and '/proc'
filesystem. Check if a process with a PATTERN cmdline is available on a NODE.
Note that FULL? option is not used at the time (the procedure always perform
full search.) Return two values: a check result and a return code."
(define (make-command ptrn)
(format #f "\
echo '
for p in $(ls /proc); do
if [[ \"$p\" =~~ ^[0-9]+ ]]; then
name=$(cat \"/proc/$p/status\" 2>/dev/null | head -1);
if [[ \"$name\" =~~ Name:.*guile ]]; then
cmdline=$(cat \"/proc/$p/cmdline\");
if [[ \"$cmdline\" =~~ ~a ]]; then
echo $p
exit 0;
fi;
fi;
fi;
done;
exit 1;
' | bash
" ptrn))
(let ((ptrn (string-append (regexp-substitute/global #f " " pattern
'pre "?" 'post)
".*")))
(rexec session (make-command ptrn))))
(define* (fallback-pkill session pattern #:key (full? #f)
(signal 'SIGTERM))
"Guile-SSH implementation of 'pkill' that uses pure bash, '/proc' filsystem
and Guile itself to kill a process. 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-values (((pids exit-status) (fallback-pgrep session pattern)))
(format-log 'functions "[scm] fallback-pkill"
"pids: ~a (pgrep exit status: ~a)"
(car pids) exit-status)
(let ((cmd (format "guile -c '(kill ~a ~a)'" (car pids) signal)))
(format-log 'functions "[scm] fallback-pkill"
"going to use this kill command: ~a" cmd)
(rexec session cmd))))
(define (command-available? session command)
"check if COMMAND is available on a remote side."
(receive (result rc)
(which session command)
(zero? rc)))
(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.
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