Shell笔记1-变量替换

变量替换

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

例：

variable_1=\"I love you , Do you love me\"

~$ var1=${variable_1#*ov}~$  echo $var1~$ e you, Do you love me

~$ var2=${variable_1##*ov}~$ echo $var2~$ e me

1. ${变量%匹配规则} # 从尾开始匹配， 最短删除
2. ${变量%匹配规则} # 从尾开始匹配， 最长删除

例：

~$ var3=${variable_1%ov*}~$ echo  $var3~$ I love you, Do you l

~$ var4=${variable_1%%ov*}~$ echo  $var4~$ I l

1. ${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
2. ${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

例：

echo  $PATH/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

~$ var5=${PATH/bin/BIN}~$ echo $var5/usr/local/sBIN:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

~$ var6=${PATH//bin/BIN}~$ echo $var6/usr/local/sBIN:/usr/local/BIN:/usr/sBIN:/usr/BIN:/sBIN:/BIN:/usr/games:/usr/local/games:/snap/BIN