Use _exit() instead of exit() so our writer process doesn't flush out
[mmh] / test / format /
drwxr-xr-x   ..
-rwxr-xr-x 595 test-localmbox
-rwxr-xr-x 715 test-myhost
-rwxr-xr-x 1003 test-mymbox
-rwxr-xr-x 808 test-myname