This document provides an introduction to common command line interface (CLI) tools including grep, sed, awk, and xargs. It explains that grep fetches lines containing a search term, sed replaces text within lines, awk processes output by columns, and xargs pipes output to command line arguments. The document demonstrates examples of each tool and how they can be combined in pipelines to extract and transform text for tasks like analyzing log files or creating a storage pool.

1. An Intro to CLI Wizardry
grep, sed, awk, and xargs
This presentation is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
(C) 2018 jim@openoid.net
Jim Salter
Technomancer,
Mercenary Sysadmin,
Small Business Owner
Today's slides can be found at:
http://openoid.net/presentations/

2. It took me 8 of my 20 years
just to believe this stuff was real
me@box:~$ awk '{print $9,
$1, $7}' httpd-access.log |
egrep '^302' | sed
's/?.*$//' | uniq -c |
sort -nr | head
153 302 54.175.189.223 /index.php
72 302 54.175.189.223 /index.php
67 302 2a01:4f8:10b:2791::2 /index.php
50 302 34.201.164.6 /index.php
48 302 34.201.161.201 /index.php
41 302 34.207.212.223 /index.php
40 302 54.175.189.223 /index.php
35 302 2a01:4f8:10b:2791::2 /index.php
34 302 34.207.212.223 /index.php
34 302 34.201.164.6 /index.php

3. Basic Redirection
none of this makes sense w/o pipes
Pipes take the OUTPUT
of one program, and feed
it to the INPUT of
another.
me@box:~$ echo code
code
me@box:~$ echo code | tr a-z A-Z
CODE

4. Sysadmins’ Reagents
these are your heavy hitters
* grep
* sed
* awk
* xargs

5. grep on the CLI
cat presentation | grep grep
grep fetches
any line of data
which contains
the thing you
asked it for.

6. grep on the CLI
cat presentation | grep grep
me@box:~$ cat knight
A novice was trying to fix a broken
Lisp machine by turning the power
off and on.
Knight, seeing what the student was
doing, spoke sternly: “You cannot
fix a machine by just power-cycling
it with no understanding of what is
going wrong.”
Knight turned the machine off and
on.
The machine worked.

7. grep on the CLI
cat presentation | grep grep
me@box:~$ cat knight | grep worked
The machine worked.
me@box:~$ cat knight | grep -c the
3
me@box:~$ cat knight | grep -ci the
4

8. (e)grep on the CLI
cat presentation | grep grep
me@box:~$ grep -irc power .
./sussman:0
./drescher:0
./moon:0
./knight:2
me@box:~$ egrep -rc ‘power|Power’ .
./sussman:0
./drescher:0
./moon:0
./knight:2

9. sed on wikipedia
shut up shut up shut up shut up
“sed (stream editor) is a Unix utility that
parses and transforms text, using a simple,
compact programming language. sed was
developed from 1973 to 1974 by Lee E.
McMahon of Bell Labs,[1] and is available
today for most operating systems.[2] sed was
based on the scripting features of the
interactive editor ed ("editor", 1971) and the
earlier qed ("quick editor", 1965–66). sed was
one of the earliest tools to support regular
expressions, and remains in use for text
processing, most notably with the substitution
command. Other options for doing "stream
editing" include AWK and Perl.”

10. sed on the CLI
stream editor. yep.
sed replaces
one thing with
another.

11. sed on the CLI
stream editor. yep.
me@box:~$ ls
cat.jpg
cat.png
cat-cat-cat.gif
me@box:~$ ls | sed ‘s/cat/dog/’
dog.jpg
dog.png
dog-cat-cat.gif
me@box:~$ ls | sed ‘s/cat/dog/g’
dog.jpg
dog.png
dog-dog-dog.gif

12. awk on wikipedia
shut up shut up shut up shut up
“The AWK language is a data-driven scripting
language consisting of a set of actions to be
taken against streams of textual data – either
run directly on files or used as part of a
pipeline – for purposes of extracting or
transforming text, such as producing
formatted reports. The language extensively
uses the string datatype, associative arrays
(that is, arrays indexed by key strings), and
regular expressions. While AWK has a limited
intended application domain and was
especially designed to support one-liner
programs, the language is Turing-complete,
and even the early Bell Labs users of AWK
often wrote well-structured large AWK
programs.”

13. awk on the CLI
was that so freaking hard?
awk is for
processing
output data
by columns.

14. awk on the CLI
btw, that’s an auk, not an awk
me@banshee:~$ echo code goes here
code goes here
me@banshee:~$ echo code goes here
| awk ‘{print $1}’
code
me@banshee:~$ echo code goes here
| awk ‘{print $1,”went”,$3}’
code went here
me@banshee:~$ echo code,goes,here
| awk -F, ‘{print $2}’
goes

15. awk on the CLI
btw that’s an auk, not an awk
me@banshee:~$ cat file
1.1 2.2 3.3 4.4
1.1 2.2 3.3 4.4
1.1 2.2 3.3 4.4
1.1 2.2 3.3 4.4
me@banshee:~$ cat file | awk
‘{mysum += $3} END {print mysum}’
13.2

16. xargs on the CLI
tinydog --stilts=cheeseburger{4}
xargs is for
piping output
to arguments.

17. Putting it all together
(this may get confusing, sorry)

18. put it together: grep
♬ so you wanna build a zpool ♬
root@box:~# ls -l /dev/disk/by-id | egrep 'foo|bar|baz'
lrwxrwxrwx 1 root root 10 Feb 19 09:52
wwn-0x50014ee206fd9549 -> ../../sdfoo
lrwxrwxrwx 1 root root 10 Feb 19 09:52
wwn-0x50014ee206fd9550 -> ../../sdbar
lrwxrwxrwx 1 root root 10 Feb 19 09:52
wwn-0x50014ee206fd9551 -> ../../sdbaz

19. put it together: awk
♬ so you wanna build a zpool ♬
root@box:~# ls -l /dev/disk/by-id | egrep 'foo|bar|baz'
| awk ‘{print $9}’
wwn-0x50014ee206fd9549
wwn-0x50014ee206fd9550
wwn-0x50014ee206fd9551

20. put it together: sed
♬ so you wanna build a zpool ♬
root@box:~# ls -l /dev/disk/by-id | egrep 'foo|bar|baz'
| awk ‘{print $9}’
| sed ‘s#^#/dev/disk/by-id/#
/dev/disk/by-id/wwn-0x50014ee206fd9549
/dev/disk/by-id/wwn-0x50014ee206fd9550
/dev/disk/by-id/wwn-0x50014ee206fd9551

21. ZOMG IT’S A ZPOOL!
♬ so you wanna build a zpool ♬
root@box:~# ls -l /dev/disk/by-id | egrep 'foo|bar|baz'
| awk ‘{print $9}’
| sed ‘s#^#/dev/disk/by-id/#
| xargs zpool create mypool
-- makes this happen --
zpool create mypool
/dev/disk/by-id/wwn-0x50014ee206fd9549
/dev/disk/by-id/wwn-0x50014ee206fd9550
/dev/disk/by-id/wwn-0x50014ee206fd9551

22. Questions?
Comments?
Angry denunciations?
https://github.com/jimsalterjrs/network-testing