CaloTech. Bash Everywhere, The Receipe Of Progressive To Mastery; Like Javascript;

Keep writing one type of lang even when you have got bored, and keep spreading mind to different perspectives of the lang leads to deeper impression.

Bash:

1. how to declare variable;

2. how to declare array; either declare an array name declare -a arr; or use assignment; += to add to array; unset $arr[2] to delete; $arr[@]/$arr[*] to represent all members of array;(el1 el2), {el3,el4,el5}, bash version; declare revelant array, declar -A relevantArray only available above bash version 4?, arr[0]; traverse: for i in ${arra[*]}; get length of array: echo ${#array1[@]},

array[index_abc]=33; echo $array[index_abc];

3. for (( ; ; )); do sth;done;, double brackets; white space everywhere; if sth;then sth; fi;

4. check operators: -eq, -gt -lt, -d, -f, ! , -nt, -ot, -n, `expr length astring`

5. sleep 5, by default by second;

6. read user input: echo "pls input:" ;read avariable; echo $avariable;

7. bash case $userinput in Y|y)echo $userinput;;in N|n)echo "n";; esac

#Example for bash split string by Symbol (comma) read -p "Enter Name, City and Age separated by a comma: " entry #reading string value IFS=',' #setting comma as delimiter read -a strarr <<<"$entry" #reading str as an array as tokens separated by IFS

readarray -d : -t strarr <<<"$str" #split a string based on the delimiter ':'

d=`date +%m-%d-%Y`

echo "Do you know Java Programming?" read -p "Yes/No? :" Answer case $Answer in Yes|yes|y|Y) echo "That's amazing." echo ;; No|no|N|n) echo "It's easy. Let's start learning bash." ;; esac

[[]]] supports regular expression

chmod o+w,o+x aa.sh

ref:

https://www.yiibai.com/bash/quotes-in-bash.html