[Shell Script] 쉘스크립트 기본 및 학습자료

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# 스크립트 실행 방법

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echo "hello world"

printf "hello world"

printf "%s %s" hello world

 

두 가지 방법으로 bash 파일을 실행 가능

# 첫번째 방법

$ bash test.sh

 

# 두번째 방법

$ chmod a+x test.sh

$ ./ test.sh

 

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# 주석처리

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#!/bin/bash

val=25

 

# Comment - print value

echo $val

 

# Multiline comment

: '

multiline comment

multiline comment

multiline comment

multiline comment

multiline comment

'

echo $val

 

# output

$ bash test.sh

25

25

 

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# 스크립트 auto indent (줄맞춤)

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# vim에서 gg=G를 입력한다.

gg - go to beginning of the file

G - go to end of the file

= - indent

 

# vimrc 설정

set sw=4

filetype indent on

 

# Reference

https://unix.stackexchange.com/questions/19945/auto-indent-format-code-for-vim

https://www.unix.com/unix-for-dummies-questions-and-answers/87221-vi-auto-indent-whole-file-once.html

 

# vscode에서 plugin을 설치

Shift + Option + F

 

# Reference

https://marketplace.visualstudio.com/items?itemName=foxundermoon.shell-format

https://marketplace.visualstudio.com/items?itemName=shakram02.bash-beautify

 

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# 쉘스크립트 문법 체크

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아래 사이트에서 문법이 잘못된 부분을 체크해준다.

https://www.shellcheck.net/

 

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# 디버깅 - set 옵션들 (-e, -u, -x)

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set은 쉘의 옵션을 설정하는 명령어이다.

-e, -u 옵션을 설정하면 스크립트에서 문제가 발생한것을 찾을수 있다.

* -e: 쉘 스크립트 실행 중에 0이 아닌 값으로 exit을 한 명령이 있으면 나머지 스크립트를 실행하지 않은 채 exit한다.

* -u: 정의되지 않은 변수(undefined)를 참조하면 에러를 출력하며 바로 exit한다.

* -x: 쉘 스크립트가 실행하는 모든 명령을 화면에 출력한다. 디버깅에 유용하다.

 

# 쉘스크립트의 도입부에 다음과 같이 적으면 된다.

set -e -u -x

 

# bash xxx.sh 실행시 옵션 적용

bash -x xxx.sh

bash -eux xxx.sh

 

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# shell command 실행

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#!/bin/bash

# use backticks " ` ` " to execute shell command

echo `date`

 

# executing bash command without backticks

echo date

 

# use #(command)

echo $(date)

 

# shell execution

echo "I'm in $(pwd)"

echo "I'm in `pwd`"

 

# output

$ bash test.sh

2021년 4월 10일 토요일 04시 10분 28초 KST

date

2021년 4월 10일 토요일 04시 10분 28초 KST

I'm in /src/shell

I'm in /src/shell

 

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# 스크립트 디렉토리와 이름 출력

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#!/bin/bash

# Get the location where this script is located since it may have been run from any folder

scriptFolder=$(cd $(dirname "$0") && pwd)

# Also determine the script name, for example for usage and version.

# - this is useful to prevent issues if the script name has been changed by renaming the file

scriptName=$(basename $scriptFolder)

 

echo "scriptFolder: $scriptFolder"

echo "scriptName: $scriptName"

 

# output

$ bash test.sh

scriptFolder: /Users/src/shell

scriptName: test.sh

 

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# 마지막 작업의 종료 상태 확인

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#!/bin/bash

# The following will always fail because the file does not exist.

fileToRemove="/tmp/some-file-that-does-not-exist"

 

# Redirect error to /dev/null so script message is used instead.

rm "$fileToRemove" 2> /dev/null

if [ $? -eq 0 ]; then

echo "Success removing file: $fileToRemove"

else

echo "File does not exist: $fileToRemove"

fi

 

# output

$ bash test.sh

File does not exist: /tmp/some-file-that-does-not-exist

 

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# 학습자료들

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# 핵심 요약 자료

https://blog.gaerae.com/2015/01/bash-hello-world.html

http://programmingexamples.wikidot.com/bash-scripting

https://linuxconfig.org/bash-scripting-tutorial

 

# cheetsheet

https://devhints.io/bash

 

# tutorial

https://linuxhint.com/30_bash_script_examples/

https://linuxconfig.org/bash-scripting-tutorial

http://learn.openwaterfoundation.org/owf-learn-linux-shell/useful-scripts/useful-scripts/

 

# template

https://betterdev.blog/minimal-safe-bash-script-template/

https://github.com/ralish/bash-script-template/blob/main/template.sh

https://natelandau.com/boilerplate-shell-script-template/

https://jonlabelle.com/snippets/view/shell/another-bash-script-template

http://mars.tekkom.dk/w/index.php/Bash_script_template

https://dev.to/thiht/shell-scripts-matter

 

# example

https://www.tecmint.com/linux-server-health-monitoring-script/

 

# youtube

https://www.youtube.com/watch?v=RIKJVIcYNqE&list=PLYRfEO8DA8gikpkXw8wF8kJZDod2lFrML&index=1

https://www.youtube.com/watch?v=08XnZ8YA8MU&list=PLTJfebMjBKSLv0yQrgCOBLZtvBBD5lWqu&index=1

https://www.youtube.com/watch?v=035pZp2R50M

https://www.youtube.com/watch?v=RdY7wiCPN-Q

https://www.youtube.com/watch?v=GtovwKDemnI

https://www.youtube.com/watch?v=e7BufAVwDiM

https://www.youtube.com/watch?v=cQepf9fY6cE&list=PLS1QulWo1RIYmaxcEqw5JhK3b-6rgdWO_

 

# 참고 자료

http://mug896.github.io/bash-shell/

https://linuxhint.com/category/bash-programming/

https://github.com/awesome-lists/awesome-bash

https://github.com/alebcay/awesome-shell

https://awesomerank.github.io/lists/alebcay/awesome-shell.html