flush output in Bourne Shell

Question

I use echo in Upstart scripts to log things:

script
    echo "main: some data" >> log
end script

post-start script
    echo "post-start: another data" >> log
end script

Now these two run in parallel, so in the logs I often see:

main: post-start: some data another data

This is not critical, so I won't employ proper synching, but thought I'd turn auto flush ON to at least reduce this effect. Is there an easy way to do that?

Update: yes, flushing will not properly fix it, but I've seen it help such situations to some degree, and this is all I need in this case. It's just that I don't know how to do it in Shell

Answer 1

Why do you assume that flushing would help? The write done by echo includes a newline, so if the first script ran to completion before the second, the newline would already by there.

In the output it isn't, which indicates that the second script was run before the first was complete, thus interleaving their outputs.

Flushing won't help with this, it's a "proper" parallel race condition.

Answer 2

Try changing:

echo "text"

To:

cat << EOF
text
EOF