Add is_package_installed function to know if a package is installed

This helps reduce the distro-dependent code in stack.sh, and also fixes
the bug where "rpm -qa | grep sudo" will work if gnome-sudoku is
installed.

Rebased

Change-Id: Ib1330b29b915b41d9724197edd791f0d4e0fe373

functions

@@ -548,6 +548,26 @@ function install_package() {
 }
 
 
+# Distro-agnostic function to tell if a package is installed
+# is_package_installed package [package ...]
+function is_package_installed() {
+    if [[ -z "$@" ]]; then
+        return 1
+    fi
+
+    if [[ -z "$os_PACKAGE" ]]; then
+        GetOSVersion
+    fi
+    if [[ "$os_PACKAGE" = "deb" ]]; then
+        dpkg -l "$@" > /dev/null
+        return $?
+    else
+        rpm --quiet -q "$@"
+        return $?
+    fi
+}
+
+
 # Test if the named environment variable is set and not zero length
 # is_set env-var
 function is_set() {

stack.sh

@@ -182,11 +182,7 @@ if [[ $EUID -eq 0 ]]; then
     sleep $ROOTSLEEP
 
     # Give the non-root user the ability to run as **root** via ``sudo``
-    if [[ "$os_PACKAGE" = "deb" ]]; then
-        dpkg -l sudo || install_package sudo
-    else
-        rpm -qa | grep sudo || install_package sudo
-    fi
+    is_package_installed sudo || install_package sudo
     if ! getent group stack >/dev/null; then
         echo "Creating a group called stack"
         groupadd stack
@@ -215,12 +211,7 @@ if [[ $EUID -eq 0 ]]; then
     exit 1
 else
     # We're not **root**, make sure ``sudo`` is available
-    if [[ "$os_PACKAGE" = "deb" ]]; then
-        CHECK_SUDO_CMD="dpkg -l sudo"
-    else
-        CHECK_SUDO_CMD="rpm -q sudo"
-    fi
-    $CHECK_SUDO_CMD || die "Sudo is required.  Re-run stack.sh as root ONE TIME ONLY to set up sudo."
+    is_package_installed sudo || die "Sudo is required.  Re-run stack.sh as root ONE TIME ONLY to set up sudo."
 
     # UEC images ``/etc/sudoers`` does not have a ``#includedir``, add one
     sudo grep -q "^#includedir.*/etc/sudoers.d" /etc/sudoers ||

tests/functions.sh

@@ -239,3 +239,44 @@ test_disable_negated_services 'a,-a' ''
 test_disable_negated_services 'b,a,-a' 'b'
 test_disable_negated_services 'a,b,-a' 'b'
 test_disable_negated_services 'a,-a,b' 'b'
+
+
+echo "Testing is_package_installed()"
+
+if [[ -z "$os_PACKAGE" ]]; then
+    GetOSVersion
+fi
+
+if [[ "$os_PACKAGE" = "deb" ]]; then
+    is_package_installed dpkg
+    VAL=$?
+else
+    is_package_installed rpm
+    VAL=$?
+fi
+if [[ "$VAL" -eq 0 ]]; then
+    echo "OK"
+else
+    echo "is_package_installed() on existing package failed"
+fi
+
+if [[ "$os_PACKAGE" = "deb" ]]; then
+    is_package_installed dpkg bash
+    VAL=$?
+else
+    is_package_installed rpm bash
+    VAL=$?
+fi
+if [[ "$VAL" -eq 0 ]]; then
+    echo "OK"
+else
+    echo "is_package_installed() on more than one existing package failed"
+fi
+
+is_package_installed zzzZZZzzz
+VAL=$?
+if [[ "$VAL" -ne 0 ]]; then
+    echo "OK"
+else
+    echo "is_package_installed() on non-existing package failed"
+fi