Add return code support to pid.

Test: pid nonexistent; echo $?
Test: pid --exact nonexistent; echo $?
Change-Id: If8efb1ca27ae3ed7b5be1c51179fae387c56e305

scripts/pid

@@ -14,22 +14,29 @@
 # limitations under the License.
 
 # Get the pid of processes matching a string.
-prepend=''
-append=''
+EXACT=0
 if [ "$1" = "--exact" ]; then
-    prepend=' '
-    append='$'
+    EXACT=1
     shift
 fi
+
 EXE="$1"
-if [ "$EXE" ] ; then
-    PID=`adb shell ps \
-        | tr -d '\r' \
-        | \grep "$prepend$EXE$append" \
-        | sed -e 's/^[^ ]* *\([0-9]*\).*$/\1/'`
-    echo "$PID"
-else
+if ! [ "$EXE" ] ; then
     echo "usage: pid [--exact] <process name>"
     exit 255
 fi
 
+if [ $EXACT == 1 ]; then
+    PIDS="$(adb shell pidof $EXE)"
+    RC=$?
+else
+    PIDS=$(adb shell "ps -o PID,NAME | tail -n +1 | grep $EXE | tr -s ' ' | cut -f2 -d' '")
+    [ -n "$PIDS" ]
+    RC=$?
+fi
+
+for PID in $PIDS; do
+    echo $PID
+done
+
+exit $RC