4 ms·
> How do you easily fork to run a command in the background? `turtle` provides `fork` for running a command in the background. Example usage: example = d
by Gabriel439 12y ago
> How do you easily fork to run a command in the background?
`turtle` provides `fork` for running a command in the background. Example usage:
example = do
using (fork commandToForkInAnotherThread)
theseCommandsStillRunInTheOriginalThread
> How does setting up pipes work?
See the `inproc` and `inshell` commands, which let you convert any shell command into a stream transformation embedded within Haskell.
> What's the idiom for chdir'ing to a subdirectory such that you pop back out again when you're done (I'd use a subshell with (ch xxx; ...) in bash)?
You can write a combinator for this using `turtle` pretty easily:
pushd newDir = do
oldDir <- pwd
cd newDir
return (cd oldDir)
... and you use it like this:
example = do
popDir <- pushDir "/tmp"
... do stuff ...
popDir
> what's the equivalent of <() in bash?
`inproc`/`inshell` which let you read in a command's standard output as a stream
- deleted 12y ago[deleted]
- barrkel 12y agoFWIW: <(foo) in bash creates a fifo, and pipes the output of foo to the fifo. It then replaces the whole <(foo) argument with the path to the fifo. This means that commands that normally expect to read from a file on the command line can instead be wired to read their input from a process. And, of course, both processes run concurrently. >(foo) does the same thing, except the other way around, for process output.
- danidiaz 12y agoThere is a "createPipe" function in the "unix" package http://hackage.haskell.org/package/unix-2.7.1.0/docs/System-Posix-IO.html#v:createPipe http://hackage.haskell.org/package/unix-2.7.1.0/docs/System-... that gets us half-way towards process substitution. Unfortunately, I don't know how to get the name of the device file associated to the pipe, and I need it in order to pass it as an argument to the reading process :(
- thinkpad20 12y agoIn my opinion it be nice to write it as a wrapper type thing: inDir d action = do oldDir <- pwd cd newDir result <- action cd oldDir return result Then you could use it like a python `with` statement. :)