Check in linux start script whether gbm is running

Fix #112 for linux

gbm.sh

@@ -1,22 +1,45 @@
 #!/bin/sh -e
-#check for all dependencies
-for prog in mono readlink df 7za;do
-    [ -n "`whereis -b ${prog} | cut -sd' ' -f2`" ] || (echo "Please install ${prog}" && exit 1);
-done
-for lib in libsqlite3;do
-    [ -n "`ldconfig -p | grep ${lib}`" ] || (echo "Please install ${lib}" && exit 1);
-done
-dir="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)"
-echo "Located in ${dir}";
-gbmpath='./';
-#locate GBM.exe
-if [ "${dir}" = '/usr/bin' ] && [ -s '/usr/share/gbm/GBM.exe' ]; then
-    gbmpath='/usr/share/gbm/';
-elif [ "${dir}" = '/usr/local/bin' ] && [ -s '/usr/local/share/gbm/GBM.exe' ]; then
-    gbmpath='/usr/local/share/gbm/';
-elif [ ! -s './GBM.exe' ]; then
-    echo 'GBM.exe not found';
-    exit 2;
+# prepare 
+if [  -z "${XDG_DATA_HOME}" ]; then
+    XDG_DATA_HOME="${HOME}/.local/share"
+fi
+mkdir -p "${XDG_DATA_HOME}/gbm"
+pidfile="${XDG_DATA_HOME}/gbm/pid"
+
+# check whether pid file exists and process is running
+if ( ! [ -e "${pidfile}" ] || ! pgrep -F "${pidfile}" ); then
+
+    # check for all dependencies
+    for prog in mono readlink df 7za;do
+        [ -n "`whereis -b ${prog} | cut -sd' ' -f2`" ] || (echo "Please install ${prog}" && exit 1);
+    done
+    for lib in libsqlite3;do
+        [ -n "`ldconfig -p | grep ${lib}`" ] || (echo "Please install ${lib}" && exit 1);
+    done
+
+    # directory this script is located in
+    dir="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)"
+    echo "Located in ${dir}";
+    gbmpath='./';
+
+    # locate GBM.exe
+    if [ "${dir}" = '/usr/bin' ] && [ -s '/usr/share/gbm/GBM.exe' ]; then
+        gbmpath='/usr/share/gbm/';
+    elif [ "${dir}" = '/usr/local/bin' ] && [ -s '/usr/local/share/gbm/GBM.exe' ]; then
+        gbmpath='/usr/local/share/gbm/';
+    elif [ ! -s './GBM.exe' ]; then
+        echo 'GBM.exe not found';
+        exit 2;
+    fi
+
+    # pass our arguments to GBM and run it in background
+    mono --desktop "${gbmpath}GBM.exe" "$@" &
+    # store pid and wait for process to end
+    echo $! > "${pidfile}"
+    wait $!
+    rm "${pidfile}"
+    exit $?;
+else
+    echo "GBM is already running"
+    exit 1;
 fi
-mono --desktop ${gbmpath}'GBM.exe' "$@";
-exit $?;