Use type builtin to check for the existence of the curl command.

There is no need to actually execute curl in order to check that it exists on
the system, the type builtin can tell us without having to fork the command.

centos2rocky.sh

@@ -23,7 +23,7 @@ if [[ "$(id -u)" -ne 0 ]]; then
       "${errcolor}Either use sudo or 'su -c ${0}'$nocolor"
 fi
 
-if [[ "$(curl 2>/dev/null || echo $?)" == 127 ]]; then
+if ! type curl >/dev/null 2>&1; then
   printf "${blue}Curl is not installed! Installing it...$nocolor"
   dnf -y install curl libcurl
 fi