diff --git a/local/bin/dfm b/local/bin/dfm
index 3c03385..22b0c20 100755
--- a/local/bin/dfm
+++ b/local/bin/dfm
@@ -164,7 +164,9 @@ function section_brew
         menu_usage "$USAGE_PREFIX" "${MENU[@]}"
         ;;
     esac
-  } || menu_section "$USAGE_PREFIX" "brew not available on this system"
+  }
+
+  ! have brew && menu_section "$USAGE_PREFIX" "brew not available on this system"
 }
 
 function section_dotfiles
@@ -207,7 +209,8 @@ function section_dotfiles
       ;;
     yamlfmt)
       # format yaml files
-      have yamlfmt && yamlfmt -conf "$DOTFILES/.yamlfmt" || msg_err "yamlfmt not found"
+      have yamlfmt && yamlfmt -conf "$DOTFILES/.yamlfmt"
+      ! have yamlfmt && msg_err "yamlfmt not found"
       ;;
     shfmt)
       # Format shell scripts according to following rules.
diff --git a/scripts/install-gh-extensions.sh b/scripts/install-gh-extensions.sh
index d42aebc..ffba0bf 100755
--- a/scripts/install-gh-extensions.sh
+++ b/scripts/install-gh-extensions.sh
@@ -39,4 +39,7 @@ have gh && {
   done
 
   msg_ok "Done"
-} || msg_err "gh (GitHub Client) could not be found, please install it first"
+}
+
+! have gh \
+  && msg_err "gh (GitHub Client) could not be found, please install it first"
diff --git a/scripts/install-go-packages.sh b/scripts/install-go-packages.sh
index 302afd9..53f924b 100755
--- a/scripts/install-go-packages.sh
+++ b/scripts/install-go-packages.sh
@@ -34,4 +34,6 @@ have go && {
   done
 
   msg_ok "Done"
-} || msg "go hasn't been installed yet."
+}
+
+! have go && msg "go hasn't been installed yet."
diff --git a/scripts/install-npm-packages.sh b/scripts/install-npm-packages.sh
index 48371af..db4db89 100755
--- a/scripts/install-npm-packages.sh
+++ b/scripts/install-npm-packages.sh
@@ -36,4 +36,6 @@ have npm && {
   msg_run "Upgrading all global packages"
   npm -g --no-progress --no-timing --no-fund outdated
   npm -g --no-timing --no-fund upgrade
-} || msg_err "npm could not be found."
+}
+
+! have npm && msg_err "npm could not be found."
diff --git a/scripts/install-ntfy.sh b/scripts/install-ntfy.sh
index b2f491a..be10d93 100755
--- a/scripts/install-ntfy.sh
+++ b/scripts/install-ntfy.sh
@@ -6,9 +6,9 @@
 source "$HOME/.dotfiles/scripts/shared.sh"
 set -e
 
-have ntfy && {
-  msg "ntfy already installed"
-} || {
+have ntfy && msg "ntfy already installed"
+
+! have ntfy && {
   case $(dfm check arch) in
     Linux)
       NTFY_ARCH="linux_$(arch)"
diff --git a/scripts/install-xcode-cli-tools.sh b/scripts/install-xcode-cli-tools.sh
index 24044c0..7d109dd 100755
--- a/scripts/install-xcode-cli-tools.sh
+++ b/scripts/install-xcode-cli-tools.sh
@@ -4,6 +4,12 @@
 # Ismo Vuorinen <https://github.com/ivuorinen> 2018
 #
 
+[ "$(uname)" != "Darwin" ] && echo "Not a macOS system" && exit 0
+
+! have xcode-select \
+  && msg_err "xcode-select could not be found, skipping" \
+  && exit 0
+
 # Ask for the administrator password upfront
 sudo -v