reverse the order of characters in a string

Question

In string \"12345\", out string \"54321\". Preferably without third party tools and regex.

Answer 1

For those without rev (recommended), there is the following simple awk solution that splits fields on the null string (every character is a separate field) and prints in reverse:

awk -F '' '{ for(i=NF; i; i--) printf("%c", $i); print "" }'

The above awk code is POSIX compliant. As a compliant awk implementation is guaranteed to be on every POSIX compliant OS, the solution should thus not be thought of as "3rd-party." This code will likely be more concise and understandable than a pure POSIX sh (or bash) solution.

(; I do not know if you consider the null string to -F a regex... ;)