Linux+ 4.2.2: Conditions and tests

Numeric tests with exit codes, file and string tests, a regular expression match and a case statement.

Before you start

Work as root, so ~ is /root. The lab only checks that ~/diskcheck.sh doesn't exist yet. Write answers to the files in /root/lab-answers/.

Write the executable script ~/diskcheck.sh. It takes a limit in percent as its first argument (default 80) and reads how full / is. At or above the limit it prints ALERT: / is N% and exits 2; at or above the limit minus 10 it prints warn: / is N% and exits 1; otherwise it prints ok: / is N% (exit 0). Run it with no argument and with 5.
Loop over /etc/passwd, /etc, /nope and /bin, and print for each whether it is a link, dir, file or missing (as PATH: TYPE, testing for a link first). Then test an empty variable with -z (printing empty), and compare 10 and 9 as strings with [[ 10 > 9 ]] || echo "string compare says 10 < 9". Save all of the output in /root/lab-answers/2.
For 10.0.5.21, 10.0.5 and web01, print X: ipv4 or X: not ipv4 using a regular expression match. Then, for start, stop and bogus, use a case statement to print X ok for start and stop and X unknown for anything else. Save all of the output in /root/lab-answers/3.

df --output=pcent / | tail -1 | tr -dc '0-9', [ "$used" -ge "$limit" ], $((limit - 10)), exit 2.
[ -L ], [ -d ], [ -f ]; { ...; } > /root/lab-answers/2 saves the output of several commands.
[[ $ip =~ ^([0-9]{1,3}\.){3}[0-9]{1,3}$ ]]; case $a in start|stop) ...;; *) ...;; esac.