src/functions/functions.lock

   1 #!/bin/bash
   2 ###############################################################################
   3 #                                                                             #
   4 # IPFire.org - A linux based firewall                                         #
   5 # Copyright (C) 2012  Michael Tremer & Christian Schmidt                      #
   6 #                                                                             #
   7 # This program is free software: you can redistribute it and/or modify        #
   8 # it under the terms of the GNU General Public License as published by        #
   9 # the Free Software Foundation, either version 3 of the License, or           #
  10 # (at your option) any later version.                                         #
  11 #                                                                             #
  12 # This program is distributed in the hope that it will be useful,             #
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of              #
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               #
  15 # GNU General Public License for more details.                                #
  16 #                                                                             #
  17 # You should have received a copy of the GNU General Public License           #
  18 # along with this program.  If not, see <http://www.gnu.org/licenses/>.       #
  19 #                                                                             #
  20 ###############################################################################
  21
  22 function lock_acquire() {
  23         local lockfile="${1}"
  24         assert isset lockfile
  25
  26         # timeout value in seconds
  27         local timeout=60
  28         timeout=$(( ${timeout} * 10 ))
  29
  30         log DEBUG "Acquiring lock '${lockfile}'."
  31
  32         local free="false"
  33         while [ ${timeout} -gt 0 ]; do
  34                 if [ ! -e "${lockfile}" ]; then
  35                         free="true"
  36                         break
  37                 fi
  38
  39                 timeout=$(( ${timeout} - 1 ))
  40                 sleep 0.1
  41         done
  42
  43         assert ${free} "Could not acquire lock '${lockfile}'."
  44
  45         # Write out pid to the lockfile and make sure that
  46         # nobody else can access it.
  47         echo "$$" > ${lockfile}
  48         chmod 600 ${lockfile}
  49 }
  50
  51 function lock_release() {
  52         local lockfile="${1}"
  53
  54         log DEBUG "Releasing lock '${lockfile}'."
  55
  56         # Remove the lockfile (okay if it does not exist).
  57         rm -f ${lockfile}
  58 }