bash 预定义变量

$?

$$

$!

#!/usr/bin/env bash    
arg1=$1    
arg2=$2    
# ✅    
num=$(($arg1 + $arg2))    
# ✅    
str=$((arg1 + arg2))    
echo "num: \$arg1 + \$arg2 = $num"    
# -e 换行    
echo -e "\n"    
echo "str: arg1 + arg2 = $str"    
# DEMO    
# ./str.sh 1 2    
# num: $arg1 + $arg2 = 3    
# str: arg1 + arg2 = 3

zsh bug

https://stackoverflow.com/questions/18428374/commands-not-found-on-zsh

for loop

for i in $*

  do

     echo "参数 i" $i 

  done

#!/usr/bin/env bash

echo ? emoji ^-v-^

# -e 换行

echo -e "\n"

arg1=$1

arg2=$2

arg3=$3

arg4=$4

arg5=$5

arg6=$6

arg7=$7

arg8=$8

arg9=$9

# >= 10, $n => ${n} ✅

arg10=${10}

arg11=${11}

arg12=${12}

# arg10=$10

# arg11=$11

# arg12=$12

echo $arg1

echo $arg2

echo $arg3

echo $arg4

echo $arg5

echo $arg6

echo $arg7

echo $arg8

echo $arg9

echo $arg10

echo $arg11

echo $arg12

# ? ✅, 参数可以为空

all=$((arg1 + arg2 + arg3 + arg4 + arg5 + arg6 + arg7 + arg8 + arg9 + arg10 + arg11 + arg12))

# -e 换行

echo -e "\n"

echo $all

# DEMO

# ./dollar-args.sh 1 2 3 4 5 6 7 8 9 10 11 12

# 55 + 23 = 78

# const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];

# arr.reduce((acc, item) => acc += item, 0);

$n, $0, $1~$9, ${10}~${n}

$* , 参数整体

$@， 参数列表

$#，参数个数