标签：答案 ror hide onclick *** 对比 yarn 字符串 blog
例1：从头匹配最短删除
[root@localhost ~]# var1="I love you,Do you love me"
[root@localhost ~]# echo ${var1#*ov}
e you,Do you love me
例2：从头匹配最长删除
[root@localhost ~]# var1="I love you,Do you love me"
[root@localhost ~]# echo ${var1##*ov}
e me例3：后匹配最短删除
[root@localhost ~]# echo ${var1%ov*}
I love you,Do you l
例4：从后匹配最长删除
[root@localhost ~]# echo ${var1%%ov*}
I l
expr代表字符串，以下以string代表expr为例
注意使用expr索引下标从1开始
#当变量str未赋值时为string
[root@localhost ~]# echo ${str-string}
string#当变量str为空时为空
[root@localhost ~]# str=
[root@localhost ~]# echo ${str-string}
#当变量str赋值后为str的值
[root@localhost ~]# str=123
[root@localhost ~]# echo ${str-string}
123
以下类推，生产环境中不常用
语法1：${#string}
语法2：expr length “$string”
[root@localhost ~]# var="Hello World"
[root@localhost ~]# echo ${#var}
11
[root@localhost ~]# echo `expr length "$var"`
11
语法：expr index “$string” substr
默认时将start切割成s,t,a,r,t字符依次去在var中查找
所以uniq就被分割成u,n,i,q依次对比var变量中的第一个字符q，所以返回1
#查找start在var中的位置
[root@localhost ~]# var="quickstart is a app" [root@localhost ~]# echo `expr index "$var" start` 6
[root@localhost ~]# echo `expr index "$var" uniq`
1
语法：expr match “$string” substr
字串必须从头开始匹配
[root@localhost ~]# echo $var quickstart is a app [root@localhost ~]# echo `expr match "$var" app` 0 [root@localhost ~]# echo `expr match "$var" quicks` 6 [root@localhost ~]# echo `expr match "$var" quickstart` 10
例1：从第10位提取到最后，索引下标从0开始
效果与例4一样
[root@localhost ~]# var="kafka hadoop yarn mapreduce"
[root@localhost ~]# echo ${var:10}
op yarn mapreduce
例2：从第10位开始提取5位字符
[root@localhost ~]# echo ${var:10:5}
op ya
例3：从右往左提取5个字符，下标从1开始，注意冒号后有空格
[root@localhost ~]# echo ${var: -5}
educe
从右往左提取的5个字符中提取长度为2的字符串
[root@localhost ~]# echo ${var: -5:2}
ed
例5：从左往右第10个字符开始提取长度为5的字符串
注意使用expr下标从1开始
[root@localhost ~]# echo `expr substr "$var" 10 5` oop y
小练习答案
[root@localhost ShellScript]# cat example.sh
#!/bin/bash
string="Bigdata process framework is Hadoop,Hadoop is an open source project"
function print_tips
{
echo "***************************************"
echo "* (1) 打印string长度 *"
echo "* (2) 删除字符串中所有的Hadoop *"
echo "* (3) 替换第一个Hadoop为Mapreduce *"
echo "* (4) 替换全部Hadoop为Mapreduce *"
echo "* (5) 重新打印 *"
echo "***************************************"
}
function len_of_string
{
echo "${#string}"
}
function del_hadoop
{
echo "${string//Hadoop/}"
}
function rep_hadoop_mapreduce_first
{
echo "${string/Hadoop/Mapreduce}"
}
function rep_hadoop_mapreduce_all
{
echo "${string//Hadoop/Mapreduce}"
}
print_tips
echo "【string=$string】"
while true
do
read -p "Pls input your choice 1|2|3|4|5|q|Q :" choice
case $choice in
1)
len_of_string
;;
2)
del_hadoop
;;
3)
rep_hadoop_mapreduce_first
;;
4)
rep_hadoop_mapreduce_all
;;
5)
print_tips
;;
q|Q)
exit
;;
*)
echo "Error,input only in {1|2|3|4|q|Q}"
;;
esac
done
-d指定分隔符，默认使用tab键作为分隔符，-f取第几段
cat /etc/passwd | cut –d “:” –f 1
标签：答案 ror hide onclick *** 对比 yarn 字符串 blog
原文地址：https://www.cnblogs.com/tz90/p/12274816.html
