Bug#353911: md5sum --check checks only if _all_ are bad

[Dan Jacobson]

Package: coreutils
Version: 5.93-5
Severity: minor
File: /usr/bin/md5sum
Tags: upstream

The docs indeed say "if no valid line is found, `md5sum' exits with
nonzero status." i.e., 99999 bad lines are no big deal, all we need is
one good line and we pass the so-called "--check"!!:

$ md5sum test/*|sed 1s/./Z/|>/dev/null md5sum -c --status -w -; echo $?
md5sum: standard input: 1: improperly formatted MD5 checksum line
0
$ md5sum test/*|sed 1s/./Z/|>/dev/null md5sum -c -; echo $?
0
$ md5sum test/*|sed  s/./Z/|>/dev/null md5sum -c -; echo $?
md5sum: standard input: no properly formatted MD5 checksum lines found
1 #Oh boy, only if they are all bad can one finally get non-zero!
$ md5sum test/*|sed 1s/./Z/|>/dev/null md5sum -c --status -; echo $?
0
$ md5sum --version
md5sum (GNU coreutils) 5.93

If this all is POSIX to blame, then you had better put warnings on the
info and man pages: "Note: all it takes is one properly formatted line
(doughnut) to payoff the police force".

P.S.:
`--warn'
     When verifying checksums, warn about improperly formatted MD5
     checksum lines.  This option is useful only if all but a few lines
     in the checked input are valid.

Say why. Else it sounds like some bolts fall off sometimes maybe.