linuxexpert-practice-labs/labs/rhcsa/3-2-loops/README.md

RHCSA 3.2: Loops

Looping over the lines of a file, over files, over fields of /etc/passwd, and over arguments.

Before you start

The lab writes /root/users.txt: one user name per line, with some blank lines, and one name (dora) that already exists. Write each script where its task says and make it executable; the checks run them.

Tasks

1. Write /usr/local/bin/mkusers that creates a user for each name in /root/users.txt, skipping users who already exist, and run it. Running it again must create no duplicates and print no errors other than "already exists".
2. Write /usr/local/bin/bigfiles that prints the name and size in bytes (NAME SIZE, one per line) of every regular file directly in /etc larger than 10000 bytes. Symbolic links don't count.
3. Write /usr/local/bin/regular-users: a loop that prints the login name and home directory (NAME HOME) of every user with a UID of 1000 or more, from /etc/passwd.
4. Write /usr/local/bin/updown that pings each host name given as an argument and prints NAME up or NAME down for each.

Hints

• while read -r name; do ...; done </root/users.txt; [ -z "$name" ] and continue; id "$name".
• for f in /etc/*, [ -f "$f" ] && [ ! -L "$f" ], stat -c %s. Compare with find /etc -maxdepth 1 -type f -size +10000c.
• while IFS=: read -r name pw uid gid gecos home shell.
• for h in "$@"; ping -c1 -W1 "$h" >/dev/null 2>&1.