Migrate from HP-UX to Linux (Shell) [closed]

For the shell itself, not much at all. The HP/UX default shell for regular users, /usr/bin/sh, is a POSIX standard-compliant shell, and the bash shell that is common on Linux is mostly a superset of it. If you preferred to use ksh, in most distributions you can get the exact same shell on Linux - although it might need to be explicitly selected for installation in the package manager, and on Linux the release version of the shell is likely to be considerably newer than what it was on HP/UX so there may be some differences.

If the question is interpreted more widely to consider not just the shell itself but the command-line tools in general, it's roughly similar to transitioning from HP/UX to Oracle Solaris or IBM AIX. As a rule of thumb, the more closely the commands are involved with actual hardware, the more differences you will encounter.

On HP/UX, you may have viewed the GNU tools as optional expanded versions of corresponding basic OS tools; on Linux, GNU tools usually are the default ones.

If your command/script manipulates regular files or directories, you can probably move the script from HP/UX to Linux as-is or with very small modifications.

If it manipulates network routes or IP addresses? You might use the same commands, but the syntax and options will have significant differences.

Dealing with hardware configuration? You'll have to learn some new commands and procedures altogether.