[root@NB index]# ls

index()().html  index()().html  index()().html

index()().html   index()().html

[root@NB index]# md5sum *.html > html.md5

[root@NB index]# tail html.md5

bd34aed02df40946c5eb1e4ac298bea2  index()().html

1ac7667f0041fb3f6ec0ad0b93f0d931  index()().html

34d351ce2480038558e1b187a327861a  index()().html

1e5b310361809a527d10ed0441539a73  index()().html

98e7303d73e81784efc0470a754e4d3f  index()().html

[root@NB index]# md5sum -c html.md5

index()().html: OK

index()().html: OK

index()().html: OK

index()().html: OK

index()().html: OK

[root@NB index]# echo k >> index\(\)\(\).html

[root@NB index]# md5sum -c html.md5

index()().html: FAILED

index()().html: OK

index()().html: OK

index()().html: OK

index()().html: OK

md5sum: WARNING:  of  computed checksums did NOT match