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AbstProcDo
Asked: 2019-05-22 03:49:13 +0800 CST

Shorten or merge multiple lines of `&> /dev/null &`

  • 772

Every time starting the machine, I run the following program:

$ cat start.sh
#! /bin/bash
google-chrome &> /dev/null &
lantern &> /dev/null &
xdg-open . &> /dev/null &
emacs &> /dev/null  &
code ~/Programs/ &> /dev/null &
xdg-open ~/Reference/topic_regex.md &> /dev/null &

Cumbersome &> /dev/null &... How could I shorten the logic?

command-line bash redirect background-process

5 Answers

  1. Best Answer

    The part &> /dev/null means output redirection. You can redirect multiple commands to the same file by grouping them into a block:

    #! /bin/bash
{
google-chrome &
lantern &
xdg-open . &
emacs  &
code ~/Programs/ &
xdg-open ~/Reference/topic_regex.md &
} &> /dev/null

    The same thing, however, cannot be used to start individual commands in the background (&). Putting & after the block would mean running the whole block as a single script in the background.

    • 16

  2. I wrote a function and put it into my .bashrc to run things detached from my terminal:

    detach () 
{ 
    ( "$@" &> /dev/null & )
}

    ... and then:

    detach google-chrome
detach xdg-open ~/Reference/topic_regex.md

    And because I'm lazy, I also wrote a shortcut for xdg-open:

    xo () 
{ 
    for var in "$@"; do
        detach xdg-open "$var";
    done
}

    Because xdg-open expects exactly one argument, the function xo iterates over all given arguments and calls xdg-open for each one separately.

    This allows for:

    detach google-chrome
xo . ~/Reference/topic_regex.md
    • 14

  3. You could redirect the output for all subsequent commands with

    exec 1>/dev/null
exec 2>/dev/null
    • 5

  4. I created a special file like /dev/null with a shorter path to shorten the redirection. I used /n as the new file’s path:

    sudo mknod -m 0666 /n c 1 3

    This way you can shorten the individual lines to e.g.:

    google-chrome &>/n &

    Source: How to create /dev/null?

    • 3

  5. You could create a loop and give it the commands as arguments:

    for i in google-chrome "xdg-open ." "code ~/Programs/"; do
  $i &
done &>/dev/null

    Note that this way exactly as with the subshell approach with curly braces it’s possible to sum up the outputs and redirect all of them at once.

    • 3