[root@stu227 he]# touch he.txt
[root@stu227 he]# set -o noclobber
[root@stu227 he]# echo "123" > he.txt
bash: he.txt: cannot overwrite existing file
如果要取消限制，就把set -o 改为set +o
[root@stu227 he]# set +o noclobber
[root@stu227 he]# echo "123" > he.txt
[root@stu227 he]# cat he.txt
123
