Fix tee pipe

[wwwutz]

fix it!

when something inside the spawned build script switches to nonbuffered IO and creates very long lines ( > 64k ) the build will fail. solution: replace the tee pipe with /usr/bin/script.

[donald]

btw: Node itself seems to be the misbehaving piece (of s...) which randomly changes stdout to O_NONBLOCK. Because of this insane behavior, other people even put Node behind a wrapper, e.g. see https://github.com/cockpit-project/cockpituous/commit/159a916710af40e8bda0c1487472f8834d6b6024 where some of the related Node issues are referenced.

Is Node used by its own build system? Wouldn't be surprised about that.

[donald]

Alas, script might help, but doesn't really fix the problem:

test.sh

#! /bin/sh
./set-stdout-nonblock
xxd /dev/urandom

with set-stdout-nonblock doing the obvious ( fcntl(1,F_SETFL,O_NONBLOCK); ). This terminates after some random time, depending on the speed of the terminal. This is true for ./test.sh for ./test.sh|tee test.log and for script -c ./test.sh test.log.

With script instead of | tee we might avoid to die immediately when something tries to write more than the 64kb pipebuffer with a single write(), but the whole thing is still in an unreliable state and might terminate at random points, after stdout is broken by one of the programs called.

[donald]

< /dev/null would be good, because whatever runs in the build script might read from stdin, waiting forever or producing random results if stdin is undefined (typically on a terminal). On the other hand, there is a exec < /dev/null in most build scripts. But even with stdin redirected to something defined, behavior of scripts (e.g. complicated test units) may change, because stdout would now be to a pseudo-terminal instead of a pipe. Something we need to remember, if old scripts, which used to work, should fail.

Would it be an alternative to try a workaround in this specific build script which uses a buggy software version?

E.g. something like

# redirecting stdout/stderr to fast storage because of node O_NONBLOCK bug (references...)
L=/dev/shm/node.build.$$.log
(
    exec >$L 2>&1
    ... do whatever....
)
cat $L
rm $L

(untested)

[pmenzel]

Would stdbuf help?

stdbuf - Run COMMAND, with modified buffering operations for its standard streams.