deb-update.bash: check for the existence of binaries

Resolves: #9

bash/deb-update.bash

@@ -8,25 +8,33 @@ set -x
 # I am not sure if -y here even does anything, at least it won't work for
 # accepting suite changes for Debian when testing becomes stable.
 # Checking for updates or new packages.
-apt-get -y update
+if hash apt-get 2>/dev/null; then
+    apt-get -y update
 
 # If arguments like -y are passed to the script, they become "$@"
-apt-get "$@" upgrade --with-new-pkgs
+    apt-get "$@" upgrade --with-new-pkgs
+fi
 
 # Flatpak apps are sandboxed and should be safe to update automatically
-flatpak update --assumeyes --noninteractive
-# Flatpak's version of `apt autoremove`
-#flatpak uninstall --unused
+if hash flatpak 2>/dev/null; then
+    flatpak update --assumeyes --noninteractive
+    # Flatpak's version of `apt autoremove`
+    #flatpak uninstall --unused
+fi
 
 # Snap packages auto-update anyway though, but I like checking them while
 # doing everything else too
-snap refresh
-# so I may have some sort of an idea when snap packages have been updated
-# if they have auto-refreshed
-snap changes
+if hash snap 2>/dev/null; then
+    snap refresh
+    # so I may have some sort of an idea when snap packages have been updated
+    # if they have auto-refreshed
+    snap changes
+fi
 
 # So the local apt-file database is up-to-date.
-apt-file update
+if hash apt-file 2>/dev/null; then
+    apt-file update
+fi
 
 # I don't have flatpak or snap going to background, because I often do
 # ./deb-update.bash && poweroff