bash笔记

echo ${#name}  get length

echo ${name:1:2}   like python [1:2]

echo `expr index "$name" d`  d in name index

echo ${a[1]}  get array data

echo ${a[@]}  get all data in array

echo ${#a[@]}

annotate   #  

$#   parametri  length

for i in "$*"; do

    echo $i

done

if [ $a -eq $b ]   //the ; behide if  has no affection

then

   echo "$a -eq $b : a 等于 b"

else

   echo "$a -eq $b: a 不等于 b"

fi

notice  blank key

if it has no blank  it will be wrong

printf "%-10s %-8s %-4s\n" 姓名 性别 体重kg

format 

for var in item1 item2 ... itemN; do command1; command2… done;

$n

in function we can transmit our param in this style  $n    function name param....

ctrl h  show hidden file

0: Standard Input (STDIN) 

1: Standard Output (STDOUT) 

2: Standard Error Output (STDERR) 

ls a.txt b.txt 1>file.out 2>&1    2 error info to sdtout   correct

set param