create check_dependency function

update.sh

@@ -7,13 +7,20 @@ TAILWINDCSS_REPO_URL=https://api.github.com/repos/tailwindlabs/tailwindcss/relea
 TMP_DIR=/tmp
 BIN_DIR=/usr/local/bin
 
+check_dependency() {
+    if ! which $1 >/dev/null 2>&1; then
+        echo "$1 needs to be installed" >&2
+        exit 1
+    fi
+}
+
 ! groups | grep -E 'root|wheel|sudo' >/dev/null && echo "You need administrative privileges for this script" && exit 1
 
-! which curl >/dev/null 2>&1 && echo "curl needs to be installed" >&2 && exit 1
-! which go >/dev/null 2>&1 && echo "go needs to be installed" >&2 && exit 1
-! which jq >/dev/null 2>&1 && echo "jq needs to be installed" >&2 && exit 1
-! which tar >/dev/null 2>&1 && echo "tar needs to be installed" >&2 && exit 1
-! which xargs >/dev/null 2>&1 && echo "xargs needs to be installed" >&2 && exit 1
+check_dependency curl
+check_dependency go
+check_dependency jq
+check_dependency tar
+check_dependency xargs
 
 echo -e '\nDownloading cpolis...'
 rm -fr $CPOLIS_DIR/*