Try these shell commands at the prompt. Many of these commands have extensive optional arguments.

Display $PATH, the value of the PATH variable

The PATH environment variable stores designated paths to executables; as a result, these executables can be executed without reference to their full paths. Commonly used paths are added to this environment variable by the system at startup. Later we will see how to add additional paths to the environment variable. Executables in directories included in $PATH are often referred to as being "in the path" of the current shell.

$ echo $PATH
/usr/local/bin:/usr/bin:/bin

List the available shells in the system

The cat (concatenate) command is a standard Linux utility that concatenates and prints the content of a file to standard output (shell output). In this case, shells is the name of the file, and /etc/ is the pathname of the directory where this file is stored.

$ cat /etc/shells
/bin/sh
/bin/bash
/sbin/nologin
/usr/bin/sh
/usr/bin/bash
/usr/sbin/nologin
/bin/tcsh
/bin/csh
/usr/bin/tmux
/bin/ksh
/bin/rksh
/bin/zsh

Find the current date and time of the system

Use the date command.

$ date
Fri Nov  9 19:23:23 CST 2018

List all of your own current running processes

Use the ps command (process status). In Linux, each process is associated with a PID or process identifier.

$ ps
  PID TTY          TIME CMD
  916 pts/58   00:00:00 bash
 1531 pts/58   00:00:00 ps