The Art of Command Line (2021)
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The document discusses best practices for using the command line interface (CLI) efficiently. It provides examples of using common UNIX commands like grep, find, awk, sort, uniq, and xargs to analyze command history, filter output, run commands in parallel, and handle encoding. The document emphasizes building small, focused tools according to the UNIX philosophy and provides tips for common tasks like capturing command output, checking exit statuses, running subprocesses, and handling different operating systems. Recommendations are made for CLI productivity tools and the linter ShellCheck.
![Runs everywhere:
case "${OSTYPE}" in
# Mac
darwin*)
[ -f ~/.zshrc.osx ] && . ~/.zshrc.osx
;;
# Linux
linux*)
[ -f ~/.zshrc.linux ] && . ~/.zshrc.linux
;;
esac
13](https://image.slidesharecdn.com/deck-210222045515/85/The-Art-of-Command-Line-2021-13-320.jpg)
The Art of Command Line (2021)
- 1. The Art of Command Line 2021-02-22 Kenta Yamamoto (@i05) 1
- 2. Unix Philosophy - "The Art of UNIX Programming" (2003) 2
- 3. $ history | awk '{ print $2 }' | sort | uniq -c | awk '$1>1' | sort -r | head 791 g 172 cat 115 git 83 echo 71 brew 70 yarn 68 ll 50 dig 49 gcloud 43 jj Make each program do one thing well. To do a new job, build afresh rather than complicate old programs by adding new features. “ “ 3
- 4. For example, you have to sort the output before uniq because they only do one thing: $ history | awk '{ print $2 }' | sort | uniq -c | awk '$1>1' | sort -r | head 4
- 5. Execute a shell script: #!/usr/bin/env bash # command-ranking.sh set -euo pipefail history | awk '{ print $2 }' | sort | uniq -c | awk '$1>1' | sort -r $ chmod u+x ./command-ranking.sh $ bash ./command-ranking.sh | head 5
- 6. Interface - standard streams: STDIN STDOUT STDERR $ time curl -IL https://example.com/ 2>&1 > file.txt $ time curl -IL https://example.com/ ... curl -IL https://example.com/ 0.02s user 0.01s system 5% cpu 0.467 total 6
- 7. Parameters - $0 , $1 , $# , $@ #!/usr/bin/env bash # sample.sh cat - echo "file=$0, 1st-arg=$1, 2nd-arg=$2, arg-num=$# args=$@" $ echo "Hello" | bash $(pwd)/sample.sh foo bar baz Hello file=/Users/kyamamoto/src/bitbucket.org/i05/support/sample.sh, 1st-arg=foo, 2nd-arg=bar, arg-num=3 args=foo bar baz 7
- 8. Sounds of Silence - $? $ touch ~/tmp/sample.txt $ echo $? 0 $ mv no-such-file.txt /tmp/ mv: cannot stat 'no-such-file.txt': No such file or directory $ echo $? 1 8
- 9. Subroutine - $(command) $ curl "https://jpnic.rdap.apnic.net/ip/$(dig +short myip.opendns.com @resolver1.opendns.com)" | jq . 9
- 10. Construct argument list - xargs : $ find . -type f -name "*" ! -path '*/.svn/*' ! -path '*/.git/*' -print0 | xargs -0 grep --ignore-case --line-number 'foo' Parallel execution - xargs : $ find . -type f -not -name '*.bz2' -print0 | xargs -0 -L 1 -P $(sysctl -n hw.ncpu) bzip2 10
- 11. Multibyte encoding - nkf : $ find . -type f -name "*.txt" | xargs nkf --guess $ find . -type f -print0 | xargs -0 nkf --overwrite -w 11
- 13. Runs everywhere: case "${OSTYPE}" in # Mac darwin*) [ -f ~/.zshrc.osx ] && . ~/.zshrc.osx ;; # Linux linux*) [ -f ~/.zshrc.linux ] && . ~/.zshrc.linux ;; esac 13
- 14. Pitfall Mac - BSD or consider installing brew install gnu-sed instead $ LANG=C find . -type f -name "*" ! -path '*/.svn/*' ! -path '*/.git/*' -print0 | xargs -0 sed -i '~' -e 's///gi' Linux - GNU $ find . -type f -name "*" ! -path '*/.svn/*' ! -path '*/.git/*' -print0 | xargs -0 sed -i -e 's///gi' 14
- 15. Pitfall Mac - BSD $ LANG=C git ls-files -z | xargs -0 sed -i '' -e 's///gi'` Linux - GNU $ git ls-files -z | xargs -0 sed -i -e 's///gi' 15
- 16. Git subcommands: $ git grep 'Could not find the specified attachment on the server' 16
- 17. Release your brain resource: Easily navigate directories - go with fewer cd s! rupa/z, or wting/autojump Remote repository management - let the tool decide where to locate the cloning repositories x-motemen/ghq 17
- 19. Linter: koalaman/shellcheck: ShellCheck, a static analysis tool for shell scripts 19
- 20. $ echo "Thank you!" 20
- 21. 21