壳牌换班程序 - 这是什么？

Question

在shell中我们有命令移位,但我在一些例子中看到它给出了移位3

为什么班次后有一个数字？它有什么关系？它能做什么 ？

例:

echo “arg1= $1  arg2=$2 arg3=$3”
shift
echo “arg1= $1  arg2=$2 arg3=$3”
shift   
echo “arg1= $1  arg2=$2 arg3=$3”
shift  
echo “arg1= $1  arg2=$2 arg3=$3”
shift

输出将是:

arg1= 1 arg2=2  arg3=3 
arg1= 2 arg2=3  arg3= 
arg1= 3 arg2=   arg3=
arg1=   arg2=   arg3=

但是当我添加它时,它不能正确显示它.

Answer 1

看一下手册页,其中说:

shift [n]
    The  positional parameters from n+1 ... are renamed to $1 .... 
    If n is not given, it is assumed to be 1.

示例脚本:

#!/bin/bash
echo "Input: $@"
shift 3
echo "After shift: $@"

运行:

$ myscript.sh one two three four five six

Input: one two three four five six
After shift: four five six

这表明在换了3之后$1=four,$2=five和$3=six.