May 17, 2020

Terminal Utilities I Often Use

In this blog post, I just list a few Unixy terminal utilities I often use. If you are a terminal veteran this will be boring for you. If you rarely use the terminal, it might have a utility or two you are not aware of yet.

I’m not giving a tutorial on the commands. Google for more details or read the man pages =). It is just to let you know that these tools exist.

Toolbox Ready
Figure 1. Toolbox Ready

grep -v

I guess everyone knows grep. It is one of the tools you’ll use all the time. You are maybe not aware of the negation filter argument -v. Instead of finding the term, it excludes it.

$ printf "abc\n123\nsomething\n" | grep 123
$ printf "abc\n123\nsomething\n" | grep -v 123

For example, I use it to remove things except for the thing I want to keep. Like:

Example Remove Branches
$ git branch
* master
$ git branch | grep -v master | xargs git branch -D
Deleted branch dev-branch-1 (was 8998ebd).
Deleted branch some-other-branch (was 8998ebd).
Deleted branch something-something (was 8998ebd)


xargs allows you to take a list of inputs and turn it into arguments. For example, take a list of git branches, Docker images, etc and feed it into command line arguments. xargs expects the command and the list of flags for that command. It will add the arguments as a list at the end.

Example Remove git branches and Docker containers
$ git branch | grep -v master | xargs git branch -D
Deleted branch dev-branch-1 (was 8998ebd).
Deleted branch some-other-branch (was 8998ebd).
Deleted branch something-something (was 8998ebd)

$ docker ps -a | awk '{print $1}' | xargs docker rm
Error: No such container: CONTAINER

Sometimes the command you are using doesn’t accept multiple arguments or needs the input in a certain position. For that you can use -I{placeholder} and then use that placeholder to tell where the argument should be placed.

Specific Placeholder example
$ ls | xargs -I@ echo Hello @ Directory
Hello file1.txt Directory
Hello file2.txt Directory


awk is a text processing tool and is mighty powerful. It has its own text processing programming language. I mostly use it to join and cut columns out, because I can’t remember more specific commands for it. Basically, each column gets an implict variable starting from $1, $2, …​ $n. And $0 is the full line. With that, you can print out reformated lines. Of course, awk supports way more, like matching witch regexes, do things at the start and end of the processing, accumulating stuff, declare functions, etc. I’ll Google that on demand.

Example Format Docker image names to untag it
$ docker images | awk '{ print $1":"$2}'

I already explained how to use AWK to add extra information to logs here.


You want to keep the output of an application and watch it at the same time? tee does store the standard out a program and stores it to a file while also forwarding it to standard out. I guess the name comes from a the T shape of a pipe?

$ ./ | tee build.log
Some build status info lines
Pages and Pages of build log
Build failed!
$ grep -i error build.log


I rarely use tmux locally, but I use it all the time when I ssh into a machine. It allows you to multiplex a terminal into multiple tabs and sections. That’s why I use it when ssh-ing to have a single connection with multiple terminals. Even better, you can get disconnected, and when you reconnect use tmux attach to reconnect to your old session. Everything will be there as you left it. Awesome!

Google for tmux and you’ll find guides, like here, here, and here.

Tmux Splitting the Terminal Up
Figure 2. Tmux Splitting the Terminal Up


watch repeats a command over and over, so you can watch what is happening. Like xargs you add the command you want to run.

Example watch a directories listing
$ watch -d ls -h blog-example/
Every 2.0s: ls -h blog-example/             gamlor-t470p: Sat May 16 07:45:03 2020


netstat, ss and others

Want to know what ports are open on your machine, and what process owns that port. There are many utilities doing that. For example ss and netstat:

Examples to show listening ports
$ ss -l -p --tcp
State   Recv-Q Send-Q   Local Address:Port      Peer Address:Port   Process
LISTEN  0      0  *       users:(("java",pid=2095,fd=774))
LISTEN  0      0  *       users:(("java",pid=2095,fd=629))
LISTEN  0      0    *       users:(("java",pid=2095,fd=762))
LISTEN  0      0    *
LISTEN  0      0    *       users:(("dropbox",pid=1857,fd=88))
LISTEN  0      0   *       users:(("java",pid=2095,fd=61))
LISTEN  0      0  *       users:(("octopi-notifier",pid=1023,fd=13))
LISTEN  0      0  *       users:(("java",pid=2095,fd=900))
LISTEN  0      0  *       users:(("dropbox",pid=1857,fd=111))
LISTEN  0      0  *       users:(("dropbox",pid=1857,fd=116))

$netstat -tulpn
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0*               LISTEN      2095/java
tcp        0      0*               LISTEN      2095/java
tcp        0      0 *               LISTEN      2095/java
tcp        0      0 *               LISTEN      -
tcp        0      0 *               LISTEN      1857/dropbox
tcp        0      0*               LISTEN      2095/java
tcp        0      0*               LISTEN      1023/octopi-notifie

That’s It for Today

Maybe you saw a utility you didn’t know about.

Tags: Unix Development