A common way for Shell to intercept strings

1, get the character from the front 8, the implementation method is as follows:

a=123456789

$ expr substr $a 1 8

$ echo $a |cut-c 1-8echo $

$ echo $a |dd Bs=1 count=8 2>/dev/null

2. Interception by the specified string

(1) The first method:

A string after the last string is truncated from left to right

${varible##*string}

A string after the first string is truncated from left to right

${varible#*string}

A string after the last string is intercepted from right to left

${varible%%string*}

A string after the first string is intercepted from right to left

${varible%string*}

such as ip=192.168.1.1, install "." Segmentation

$ echo ${ip##*.} #得到的是最后一列

1

$ echo ${ip#*.} #得到的除去第一列的字符串

168.1.1

$ echo ${ip%%.*} #得到的是第一列

192

$ echo ${ip%.*} #得到的除去最后一列的字符串

192.168.1

3, get the specified length

${VARIBLE:N1:N2}: Intercepts the variable varible the N2 character starting from N1, forming a substring. You can select specific substrings by using a different form of variable extension, depending on the specific character offset and length. Try entering the following line in bash:

such as ip=192.168.1.1

$ echo ${ip:0:3}

192

$ echo ${ip:3}

.168.1.1

4. Gets the specified column

such as ip=192.168.1.1

$ echo $ip | Cut-d "."-f2

168

$ echo $ip |  Awk-f "." ' {print $} '

168

Reference: http://54rd.net/html/2015/shell_0423/110.html

This article from "Small Fish Blog" blog, declined reprint!

A common way for Shell to intercept strings