linuxexpert-practice-labs/labs/rhcsa/1-2-grep-and-regular-expressions

RHCSA 1.2: grep and regular expressions

Matching lines, dropping comments and blank lines, anchoring a pattern to the end of a line, and counting matches.

Before you start

The lab creates users grace and henry with the shell /bin/bash, and user ivan with /sbin/nologin. Write the results of tasks 2 and 3 to the files named there, so they can be checked.

Tasks

1. As root, save every line of /etc/services that contains the string ich to /root/ich.txt, in the original order.
2. Show only the active settings of /etc/ssh/sshd_config, with no comments or blank lines (the file is readable only by root: use sudo). Save that output to /root/lab-answers/2.
3. List the login names of every user whose shell is /bin/bash, one per line, in /root/lab-answers/3.
4. Count how many lines of /etc/passwd contain nologin, and save the number to /tmp/nologin-count.txt.

Hints

• grep PATTERN FILE >FILE.
• grep -v, ^#, ^$, or grep -Ev '^(#|$)'.
• grep '/bin/bash$' and cut -d: -f1, or awk -F:.
• grep -c.