Igen, ez volt a baj, teszteltem. A ciklusmagban az ssh felzabálta az stdin-t, amelyet én valójában a while-ban lévő read-nek szántam. A megoldás az ssh parancs -n kapcsolója:
-n Redirects stdin from /dev/null (actually, prevents reading from
stdin). This must be used when ssh is run in the background. A
common trick is to use this to run X11 programs on a remote
machine. For example, ssh -n shadows.cs.hut.fi emacs & will
start an emacs on shadows.cs.hut.fi, and the X11 connection will
be automatically forwarded over an encrypted channel. The ssh
program will be put in the background. (This does not work if
ssh needs to ask for a password or passphrase; see also the -f
option.)
tr '[:lower:]' '[:upper:]' <<<locsemege
LOCSEMEGE