linux系统中去掉最后一个字符或第一个字符

[root@centos7 test]# ls
a.txt
[root@centos7 test]# cat a.txt
i e s m u
w e i p q
x z u n k
e c b v y
[root@centos7 test]# sed ‘s/.$//‘ a.txt
i e s m
w e i p
x z u n
e c b v

[root@centos7 test]# cat a.txt
i e s m u
w e i p q
x z u n k
e c b v y
[root@centos7 test]# awk ‘{sub(/.$/,"")}1‘ a.txt
i e s m
w e i p
x z u n
e c b v

[root@centos7 test]# cat a.txt
i e s m u
w e i p q
x z u n k
e c b v y
[root@centos7 test]# awk ‘{printf $0 "\b \n"}‘ a.txt
i e s m
w e i p
x z u n
e c b v

[root@centos7 test]# va=abcde
[root@centos7 test]# echo $va
abcde
[root@centos7 test]# echo ${va%?}
abcd

[root@centos7 test]# cat a.txt
i e s m u
w e i p q
x z u n k
e c b v y
[root@centos7 test]# awk ‘{print substr($0,2)}‘ a.txt
 e s m u
 e i p q
 z u n k
 c b v y

[root@centos7 test]# cat a.txt
i e s m u
w e i p q
x z u n k
e c b v y
[root@centos7 test]# sed ‘s/^.//‘ a.txt
 e s m u
 e i p q
 z u n k
 c b v y