Named Pipes in Bash

[pstadler]

You can create named pipes explicitly:

    $ mkfifo ~/pipe
    $ ./background.sh > ~/pipe &
    $ tail -f ~/pipe

http://www.linuxjournal.com/article/2156

[runn1ng]

Yes, but I have always found that cumbersome and I was never sure which program has which pipe, and what will exactly happen if one of the reading/writing programs dies. (I am still not sure.)

So I am glad that what OP wrote exists.

[saljam]

There's a caveat with process substitution; the command can't seek() on the input file.

If if a command, for example, needs to do 2 passes, it'll will either have to be 'smart' enough to stick the output in a buffer or fail.

[eatitraw]

Yes, this is a problem in bash. In zsh you can use temporary files for process substitution, like this:

vimdiff =(ls /bin) =(ls /usr/bin)

You can use it even from bash:

zsh -c 'vimdiff =(ls /bin) =(ls /usr/bin)'

[dllthomas]

This and so much more is in http://www.tldp.org/LDP/abs/html - well worth perusing if you're needing to do a lot of bash.

[recuter]

Future readers, #bash on freenode says of this link:

< greybot> The infamous "Advanced" Bash Scripting Guide should be avoided unless you know how to filter out the junk. It will teach you to write bugs, not scripts. In that light, the BashGuide was written: http://mywiki.wooledge.org/BashGuide

They felt strongly enough to learn their bot of it. Keep this in mind, I haven't read much of either resource yet.

[perlgeek]

Are these really named pipes? And if yes, what are the names? Kinda looks like anonymous pipes to my untrained eyes.

[gnaritas]

They're anonymous named pipes. Do this in a shell to see the name:

    echo <(true)

[vsbuffalo]

I wrote a post about this a while back, which may be of some help to some. http://vincebuffalo.com/2013/08/08/the-mighty-named-pipe.htm...

[nkurz]

Great article, thanks! You should submit it separately if you haven't. Noticed a typo in the title that you might fix first: "Using Names Pipes"

[taway2012]

Pretty cool.

Related: anybody has ideas to achieve the following?

display the stdout of a program on the console and also write a gzipped version of stdout to a file.

I currently jump through some hoops (involving two term windows) to achieve. 'tee -a' to a named pipe in one window and in another window, 'gzip <' from that named pipe. Would prefer a single-window, single-command solution.

[ColinWright]

What's wrong with:

    cmd | tee >( gzip - > cmd.out.gz )

[runejuhl]

Something like this?

    ls -al | tee >(cat) | gzip -c

[_paulc]

ls -al | gzip -c | tee out.gz | gzip -dc

[zokier]

Very useful, hopefully I remember this when I need it next time (that being the bane of all bash cleverness). The >(foo) would benefit from some extra explanation though, currently it is not very clear how it differs from regular |foo.

[bartbes]

>(foo) turns into a file name, so it can be passed to things that absolutely want a file name to write to. And multiple occurrences of this should work as you'd expect.

[kps]

This 'bash' feature, among others, was in ksh before bash existed.

[panzi]

If I would have seen this one or two hours ago it could have spared me hate on irc://irc.freenode.net/bash