[Haskell-cafe] I/O system brokenness with named pipes
jgoerzen at complete.org
Thu Apr 10 21:34:41 EDT 2008
So I have a need to write data to a POSIX named pipe (aka FIFO). Long
story involving a command that doesn't have an option to read data
from stdin, but can from a named pipe.
I have created the named pipe from Haskell no problem.
But I can't use writeFile to write data to it. Worse, it returns:
*** Exception: /tmp/bakroller.zD0xHj/fifo: openFile: does not exist
(No such device or address)
which is completely false, as it *does* exist, and I can cat to it as
expected. The call should block until everything is read on the
I thought maybe writeFile is being weird, so I tried:
openFile "/tmp/bakroller.zD0xHj/fifo" WriteMode
There is no logical reason I can see for this behavior. In fact,
something must be going to *extra* effort to avoid writing to a named
pipe, and I can't work out why. Named pipes are a standard, useful
part of a system and shouldn't be ignored like this.
Interestingly, readFile works fine on a named pipe.
What's going on here? Am I going to have to resort to the
System.Posix interface just to be able to write to a named pipe?
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