libs/locking.lunar

#!/bin/bash
#                                                          #
# This code is written for Lunar Linux, see                #
# http://lunar-linux.org                                   #
#                                                          #
############################################################
#                                                          #
# $FUNCTIONS/locking                                       #
# includes lock_file and unlock_file functions             #
#                                                          #
# 20020526                                                 #
#                                                          #
############################################################
#                                                          #
# Copyrighted Kagan Kongar 2002 under GPLv2                #
#                                                          #
############################################################

# function: lock_file
# usage   : lock_file <absolute file name>
# purpose : locks a file or wait until. Better use as lock_file <file> && || etc
function lock_file() {
   local TEMPFILE LOCKFILE STALE_PID
   debug_msg "lock_file ($@)"
   function file_lock() {
      #locking is disabled if ln or rm not found!!
      [ -x "/bin/ln" ] || return 0
      [ -x "/bin/rm" ] || return 0

      TEMPFILE="$1.$$"
      LOCKFILE="$1.lock"

      # test permission
      if ! echo $$ > $TEMPFILE 2>/dev/null; then
        message "${PROBLEM_COLOR}You don't have permission to access" \
                "$TEMPFILE ${DEFAULT_COLOR}"
        exit 1
      fi

      # file exists?
      if [ ! -f "$1" ]; then
        touch "$1"
      fi

      # set lockfile
      if ln $TEMPFILE $LOCKFILE 2>/dev/null ; then
        rm -f $TEMPFILE
        return 0
      # failed due to other lock?
      elif [ ! -f "$LOCKFILE" ]; then
        return 1
      fi
      # stale lock?
      STALE_PID=`< $LOCKFILE`
      if [ "$STALE_PID" -le "0" ]; then
        return 1
      fi
      if kill -0 $STALE_PID 2>/dev/null; then
        rm -f $TEMPFILE
        return 1
      fi
      # yes, stale
      rm -f $LOCKFILE 2>/dev/null &&
          echo "Removed stale lock file of process $STALE_PID"
      if ln $TEMPFILE $LOCKFILE 2>/dev/null; then
        rm -f $TEMPFILE
        return 0
      fi
      rm -f $TEMPFILE
      return 1
   }

   while ! file_lock $1; do
      message "${MESSAGE_COLOR}Waiting to lock the file $1${DEFAULT_COLOR}"
      sleep 1
   done
   return 0
}


# function: unlock_file
# usage   : unlock_file <absolute file name>
# purpose : unlocks a file
function unlock_file() {
  debug_msg "unlock_file ($@)"
  #unlocking is disabled if rm not found!!
  [ -x "/bin/rm" ] || return 0
  rm -f $1.lock 2>/dev/null && return 0
  return 1
}


lin_locked()  {
  debug_msg "lin_locked ($@)"
  [     -f        /var/lock/installing.$1  ]  &&
  ps        `cat "/var/lock/installing.$1"`    |
  grep  -q  "lin"
}


solo_locked()  {
  debug_msg "solo_locked ($@)"
  for SOLO_MODULE in `cat "$SOLO"` ; do
    if lin_locked $SOLO_MODULE ; then
      message  "${PROBLEM_COLOR}lining${DEFAULT_COLOR}${MESSAGE_COLOR} of other modules is disabled during a lin ${MODULE_COLOR}$SOLO_MODULE${DEFAULT_COLOR}"
      return
    fi
  done
  false
}


current_locked() {
  debug_msg "current_locked ($@)"
  if  lin_locked  $MODULE;  then
    message  "${QUERY_COLOR}Detected lin lock file: ${FILE_COLOR}$linING${DEFAULT_COLOR}"
    message  "${MESSAGE_COLOR}Now waiting for ${MODULE_COLOR}${MODULE}${DEFAULT_COLOR}${MESSAGE_COLOR} to finish installing or for the lock to clear.${DEFAULT_COLOR}"

    while  lin_locked  $MODULE;  do  sleep  2;  done
    false
  else
    false
  fi
}