Unable to pipe the output to another tool

[fabpot]

I'm trying to use your tool to convert a Chrome CPU profile into callgrind to be able to upload it and visualize it on Blackfire.io, which is an online alternative to KCacheGrind.

If I do something like this, it works well (https://blackfire.io/profiles/7c6f85ac-8ad2-4bae-bbe7-fda21eee858f/graph):

chrome2calltree -i some.cpuprofile > some.callgrind
blackfire --slot=2 upload some.callgrind

But using a pipe like this:

chrome2calltree -i some.cpuprofile | blackfire --slot=2 upload

triggers the following error:

Error: No file provided on the command line

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: write EPIPE
    at errnoException (net.js:905:11)
    at Object.afterWrite (net.js:721:19)

[jlfwong]

Not too sure offhand what would cause that, but I'm open to accepting PRs that fix the problem!