shell变量的子串的截取/删除/替换

[root@localhost SHELL]# NAME="I am a student student"
[root# echo ${NAME//student/teacher}
I am a teacher teacher
[root# echo ${NAME/#student/teacher}
I am a student student
[root# echo ${NAME/%student/teacher}
I am a student teacher
[root# echo ${NAME/%I am /teacher}
I am a student student
[root# echo ${NAME/#I am /teacher}
teachera student student
[root# echo ${NAME/#I am a/teacher}
teacher student student
[root# echo $NAME
I am a student student
[root# 

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