Null flush

Null flush is an option (-z) to most Apertium programs (and programs compatible with Apertium stream format) that flushes the output buffer upon receiving the \0 character instead of on end-of-file. This allows programs which call Apertium externally to keep a translator online, meaning they can avoid startup time for every translation.

To see how to use this in practice, read Daemon.

Testing

If you want to test that a pipe handles null flush correctly, you can use something like:

cat <(echo -e "this here[][\n]\0is a[][\n]\0little[][\n]\0flushing test[][\n]\0") /dev/stdin | your -z | pipe -z | goes -z | here -z

where \0 are the nulls, and the [] are there because many of the tools expect a [][\n] at the end of a stream (all the deformatters put this at the end of the stream, try echo bunnymen|apertium-destxt). Use Ctrl-D (^D) to close the input that cat keeps open.

Other flush signals

Note that in CG stream format, vislcg3 uses the string "<STREAMCMD:FLUSH>" instead of a NUL byte: http://beta.visl.sdu.dk/cg3/single/#cmd-flush (cg-proc, however, uses the NUL byte like the other programs used in Apertium).