The use of shift in shell programming under Linux

Positional parameters can be moved left with the shift command. For example, shift 3 means that the original $ $ is now $ $, the original $ $ $ $ $ $ $ $ The shift command with no parameters is equal to shift 1.

Very useful UNIX command: shift. We know that for positional variables or command parameters, the number must be certain, or when the shell program does not know its number, you can assign all the arguments to the variable $*. Left-side users require the shell in the case of not knowing the number of position variables, but also one by one the parameters-processing, that is, after the $ $ $, in the back of $ $. The value of the variable before the Shfit command executes is not available after the shift command executes.

Example one:

#!/bin/bash
Until [$#-eq 0]
Todo
echo "The parameter:$1 number is:$#"
Shift
Done

Example two:

#!/bin/bash
If [$#-eq 0]
Then
echo "Usage:a2.sh parameter"
Exit 1
Fi
Sum=0
Until [$#-eq 0]
Todo
sum= ' expr $sum + $
Shift
Done
echo "sum is: $sum"

Example three:

Here's a simple script that reads:

#!/bin/sh

Until [$#-eq 0]
Todo
echo "The first parameter is: $# number of arguments:"
Shift
Perform the above procedure x_shift.sh:

[root@ay1404171530212980a0z test]#./test 11 22 33 44 55 66 77

The results appear as follows:

The first parameter is: 11 The number of parameters is: 7
The first parameter is: 22 The number of parameters is: 6
The first parameter is: 33 The number of parameters is: 5
The first parameter is: 44 The number of parameters is: 4
The first parameter is: 55 The number of parameters is: 3
The first parameter is: 66 The number of parameters is: 2
The first parameter is: 77 The number of parameters is: 1