shell编程系列1--shell脚本中的变量替换

时间:2021-04-10 14:58:46
shell编程系列1--shell脚本中的变量替换

变量替换总结:
1、${变量#匹配规则}    # 从头开始匹配,最短删除
2、${变量##匹配规则}    # 从头开始匹配,最长删除(贪婪模式)

3、${变量%匹配规则}    # 从尾开始匹配,最短删除
4、${变量%%匹配规则}    # 从尾开始匹配,最长删除(贪婪模式)

5、${变量/旧字符串/新字符串}    # 替换变量内的旧字符串为新字符串,只替换第一个
6、${变量//旧字符串/新字符串}    # 替换变量内的旧字符串为新字符串,全部替换

variable_1="i love you,do you love me"

举例:


[root@localhost ~]# variable_1="i love you,do you love me"
[root@localhost ~]# echo $variable_1
i love you,do you love me

# 从头开始删除,只删除第一个ov及ov以前的字符串
[root@localhost ~]# var1=${variable_1#*ov}
[root@localhost ~]# echo $var1
e you,do you love me

# 从头开始删除,最长删除ov及ov以前的字符串
[root@localhost ~]# var2=${variable_1##*ov}
[root@localhost ~]# echo $var2
e me

# 从尾部删除最短匹配的ov及ov后面的字符串
[root@localhost ~]# var3=${variable_1%ov*}
[root@localhost ~]# echo $var3
i love you,do you l

# 从尾部删除最长匹配的ov及ov后面的字符串
[root@localhost ~]# var4=${variable_1%%ov*}
[root@localhost ~]# echo $var4
i l

# 替换第一个小写的bin为大写的BIN
[root@localhost ~]# echo $PATH
/usr/local/go/bin:/data/golang_project/bin:/usr/java/jdk1.8.0_181-amd64/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
[root@localhost ~]# var5=${PATH/bin/BIN}
[root@localhost ~]# echo $var5
/usr/local/go/BIN:/data/golang_project/bin:/usr/java/jdk1.8.0_181-amd64/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin

# 替换所有小写的bin为大写的BIN
[root@localhost ~]# var6=${PATH//bin/BIN}
[root@localhost ~]# echo $var6
/usr/local/go/BIN:/data/golang_project/BIN:/usr/java/jdk1.8.0_181-amd64/BIN:/usr/local/sBIN:/usr/local/BIN:/usr/sBIN:/usr/BIN:/root/BIN