linuxexpert-practice-labs/labs/lpic-1/103-1-command-line

LPIC-1 103.1: Working on the command line

Quoting, exported variables, running your own scripts, builtins and programs, and searching the manual.

Before you start

The lab installs man-db and builds the manual's search index if needed. Work as root (sudo -i) unless a task says otherwise, and write answers to the files in /root/lab-answers/.

Tasks

1. Predict what each of these prints, then check: echo '$HOME', echo "$HOME", echo \$HOME, echo "It's $USER". Write the four outputs, as root, one per line in that order, to /root/lab-answers/1.
2. Set a variable, show that bash -c 'echo $var' can't see it, export it, and try again. Check it yourself: the second try prints the value.
3. Write a two-line script, hello.sh, in your home directory, make it executable with chmod +x, and run it with ./hello.sh. Then try running it by name alone, and write why that fails to /root/lab-answers/3.
4. Run type on cd, ls, echo and ssh, and compare with which. Write the ones that are shell builtins to /root/lab-answers/4.
5. Find the man page for the crontab file format (not the command) using man -k, and write how you'd open it (such as man 1 ls) to /root/lab-answers/5.

Hints

• Single quotes keep everything literal, double quotes expand $, and \ protects one character.
• export var, env | grep var.
• #!/bin/bash on line 1; echo $PATH.
• type -a; which only searches PATH.
• man -k crontab (or apropos); the number in brackets is the section.