换壳程序-这是什么? [英] Shell shift procedure - What is this?
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问题描述
在shell中,我们有命令shift,但是我在一些示例中看到了它的移位3
In shell we have the command shift, but i saw on some example its giving shift 3
为什么上班后会有一个数字?那是什么呢?它是做什么的?
Why there is a number after shift ? and what its about ? what it does ?
示例:
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,它无法正确显示它.
But when i add that, it doesn't display it correctly.
推荐答案
看看 man 页面,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: $@"
运行它:
$ myscript.sh one two three four five six
Input: one two three four five six
After shift: four five six
这表明在移位3后,分别是$1=four
,$2=five
和$3=six
.
This shows that after shifting by 3, $1=four
, $2=five
and $3=six
.
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