How to write and match regular expressions in /bin/sh script?

Question

I am writing a shell script for a limited unix-based microkernel which doesn't have bash! the /bin/sh can't run the following lines for some reasons.

if [[ `uname` =~ (QNX|qnx) ]]; then
read -p "what is the dev prefix to use? " dev_prefix
if [[ $dev_prefix =~ ^[a-z0-9_-]+@[a-z0-9_-"."]+:.*$ ]]; then

For the 1st and 3rd lines, it complains about missing expression operator, and for the 2nd line it says no coprocess! Can anyone shed light on differences between /bin/bash and /bin/sh scripts?

Answer 1

You can use this equivalent script in /bin/sh:

if uname | grep -Eq '(QNX|qnx)'; then
   printf "what is the dev prefix to use? "
   read dev_prefix
   if echo "$dev_prefix" | grep -Eq '^[a-z0-9_-]+@[a-z0-9_-"."]+:'; then
   ...
   fi
fi