Presentation given on the DevOps Exchange London meetup on 25th January 2018.

1. Make the prompt great again
Jiri Tyr & Vladimir Babichev

2. What makes the command prompt great?
● It provides useful information
● It looks nice
● It's fast

3. Shell frameworks
● Bash
○ Bash Infinity
○ Bash-it
○ ...
● ZSH
○ Oh My ZSH
○ Prezto
○ ...
All written in shell = slow!

4. How to make it run faster?

5. Write it in Go!

6. We would like to introduce you...
GBTGBT

8. GBT = Go Bullet Train
Highly configurable prompt builder for Bash and ZSH written in Go.
It's inspired by the Bullet Train theme for Oh My ZSH framework.

9. GBT

10. GBT anatomy

11. GBT anatomy

12. GBT anatomy

13. GBT
● 10 cars
○ Custom, Dir, ExecTime, Git, Hostname, Os, PyVirtEnv, Sign, Status, Time
● Over 200 environment variables
● Nerd fonts
● Packages for multiple platforms
○ Linux
■ RPM repo ... yum install gbt
■ DEB repo ... apt-get install gbt
■ AUR ... yaourt -S gbt
○ Mac
■ Brew ... brew install gbt
○ Android
■ Termux ... apt install gbt

14. GBT on Android
● Install Termux and Termux:Styling
● Select font
● Install and setup GBT
apt update
apt install gbt
PS1='$(gbt $?)'

15. Demo

16. Benchmark
cat /tmp/test.sh
BRANCH="$(git symbolic-ref HEAD)"
[ -z "$(git status --porcelain)" ] && DIRTY_ICON='%{e[38;5;2m%}✔' ||
DIRTY_ICON='%{e[38;5;1m%}✘'
[[ "$(git rev-list --count HEAD..@{upstream})" == '0' ]] && AHEAD_ICON='' || AHEAD_ICON=' ⬆'
[[ "$(git rev-list --count @{upstream}..HEAD)" == '0' ]] && BEHIND_ICON='' || BEHIND_ICON=' ⬇'
echo -en "%{e[0m%}%{e[48;5;7m%}%{e[38;5;0m%}
%{e[48;5;7m%}%{e[38;5;0m%}%{e[48;5;7m%}%{e[38;5;0m%}
%{e[48;5;7m%}%{e[38;5;0m%}${BRANCH##*/}%{e[48;5;7m%}%{e[38;5;0m%}
%{e[48;5;7m%}%{e[38;5;0m%}%{e[48;5;7m%}$DIRTY_ICON%{e[48;5;7m%}%{e[38;5;0m%}%{e[48;5;7m%
}%{e[38;5;0m%}%{e[48;5;7m%}%{e[38;5;0m%}$AHEAD_ICON%{e[48;5;7m%}%{e[38;5;0m%}%{e[48;5;7m
%}%{e[38;5;0m%}$BEHIND_ICON%{e[48;5;7m%}%{e[38;5;0m%} %{e[0m%}"

17. Benchmark
# Execution of the testing script by Bash
for N in $(seq 10); do time (for M in $(seq 100); do bash /tmp/test.sh 1>/dev/null 2>&1; done)
done 2>&1 | awk '{ total_cpu += $19; total_time += $21 } END { print "Avg CPU:
"total_cpu/NR"%; Avg time: "total_time/NR"s" }'
Avg CPU: 102%; Avg time: 1.9407s
# Execution of the testing script by ZSH
for N in $(seq 10); do time (for M in $(seq 100); do zsh /tmp/test.sh 1>/dev/null 2>&1; done)
done 2>&1 | awk '{ total_cpu += $19; total_time += $21 } END { print "Avg CPU:
"total_cpu/NR"%; Avg time: "total_time/NR"s" }'
Avg CPU: 103%; Avg time: 1.9079s
# Execution of GBT
for N in $(seq 10); do time (for M in $(seq 100); do GBT_SHELL='zsh' GBT_CARS='Git' gbt
1>/dev/null 2>&1; done) done 2>&1 | awk '{ total_cpu += $18; total_time += $20 } END { print
"Avg CPU: "total_cpu/NR"%; Avg time: "total_time/NR"s" }'
Avg CPU: 115%; Avg time: 1.8817s

18. OS Icons

19. Prompt forwarding

20. Demo

21. How does it work?
ssh myserver -t "
echo "PS1='$(gbt)'" > /tmp/.gbt;
bash --rcfile /tmp/.gbt;
rm -f /tmp/.gbt"

22. Features
● GBT executes only locally
● GBT generates a string which is then forwarded to a remote machine
● Supports forwarding of local aliases
● Integrates with SSH, Docker, Vagrant, MySQL
● Supports su and sudo

23. Limitations
● Works only with Bash
● Doesn’t support ExecTime, Git, PyVirtEnv cars

24. Contribution and support

25. Contribution and support
● Contribute
○ Create new themes (e.g. solarized)
○ Create new cars
■ SCM (e.g. Mercurial)
■ CPU load
■ ...
○ Optimize sequence string produced by GBT
○ Make tests running in parallel
● Spread the word
○ Thanks Gareth Rushgrove for advertising it in the next DevOps Weekly ;o)
● Star the project on Github
https://github.com/jtyr/gbt

26. Thank you for your attention!
Questions?