Home / ubuntu / Questions / 887134
Accepted
Arseni Mourzenko
Asked: 2017-02-26 03:15:24 +0800 CST

What is this yellow thing with a pipe? [duplicate]

  • 772

I noticed that /var/spool/nullmailer directory contains a weird trigger entity which is displayed in yellow and has a “|” suffix.

It doesn't seem to be a directory (at least I can't cd into it), and when I try to open it with vi, the console freezes.

What is that thing?

enter image description here

command-line

2 Answers

  1. Best Answer

    It is a named-pipe - one of the 7 types of file in Unix. The p in prw--w--w- confirms it is a named-pipe.

    You can write to the pipe from one side and read the data from the other side:

    $ mkfifo mypipe
$ cat mypipe

    In another terminal

    $ cat > mypipe
Hello from the other side
What's up?

    Whatever you type in here will appear in the other terminal.

    l is an alias to ls -CF and ll is alias to ls -alFh.
    According to the man page

    -F, --classify
    append indicator (one of */=>@|) to entries

    So for a named-pipe | is appended to the filename.

    • 41

  2. You can identify any 'file' on a linux system by using the command file, followed by the file name.

    file "trigger"

    Would tell you it's a named pipe.

    • 3