linuxexpert-practice-labs/labs/lpic-1/105-2-shell-scripts/README.md

LPIC-1 105.2: Writing simple scripts

Tests and exit codes, a script that mails root, loops and case.

Before you start

The lab puts the chapter's diskcheck script in /usr/local/sbin/diskcheck. It sets aside root's mailbox, if there is one, so the check sees only new mail. Write your scripts in /root, start each with a #! line, and make them executable.

Tasks

1. Write /root/checkfiles.sh, which takes any number of file names and prints one line for each: the name and whether it's missing, a directory or a readable file. It exits with status 1 if any were missing, and 0 otherwise.
2. Install a mail client and a local MTA (Postfix), then run /usr/local/sbin/diskcheck 5 as root and read root's mail.
3. Write /root/count.sh, which prints the numbers 1 to 10, one per line, with a while loop and a counter (the chapter's for i in $(seq 1 10) rewritten).
4. Write /root/service.sh, a case script that accepts start, stop and status (printing what it would do), and prints a usage message for anything else, including no argument.

Hints

• "$@", [ -e ], [ -d ], [ -r ], exit 1; test with echo $?.
• The mail client is s-nail on the RHEL family and mailutils on Debian and Ubuntu; it gives you mail. Postfix needs to be running. mail with no arguments reads your mailbox.
• i=1, while [ "$i" -le 10 ], i=$((i + 1)).
• case "$1" in start) ... ;; *) echo "usage: ..." ;; esac; then bash -x /root/service.sh start to follow it step by step.