Did you know? Many Linux system services & login under Linux/Unix OS consult /etc/shells file. It contains a list of login shells on the system. Applications use this file to determine whether a shell is valid. Setting the wrong shell path will deny login.

Read more: Understanding the /etc/shells file

Searching multiple words like a pro on your macOS, Linux and Unix box

When you type ‘rsync –help’ you get a wall of text. One option is to use less on Linux:

rsync –help|less

But, I prefer to grep to search multiple strings to find about -p, -h, -i, -b & -u options:

rsync –help|grep -E -w – ’-(p|h|i|b|u)’

SeeHow To Search Multiple Words / String Pattern Using grep Command on Bash shell for more info.

In order to tell grep not to treat ’–’ as command line option prefix pattern with –. The double dash “–” means “end of command line flags.” It tells grep (or any valid Linux/Unix command) not to try to parse what comes after command line options. See What Does ‐‐ (double dash) Mean In SSH Shell Command? for more info