Ubuntu – What does “[[ $- != i ]] && return” mean

bashrccommand line

I have this line in my .bashrc and I would like to know what exactly this means

# If not running interactively, don't do anything
[[ $- != *i* ]] && return

Best Answer

$- means 'current flags'.
echo $- returns "himBH". Those are all defaults.
so ... [[ $- != *i* ]] && return actually does what it says above in a comment: it checks if the interactive flag is set. The [[ and ]] make it a boolean so it ends up in a "true" or "false". "false && return" makes it go on "true && return" makes it execute the return.

The default flags explained in more detail:

h is for "hash all": this tells bash to remember the locations of commands it has found through querying your PATH.

i is for "interactive": entering input & getting back output.

m is for "monitor": this enables job control

B is for "brace expand". This allows you to use brace expansion

H is for "history expand". This is what enables you to rerun a command from your history by prefacing its number with an exclamation point

By the way. I have ...

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;
esac

Basically does the same but easier to read I assume.

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Ubuntu – What does `ls –author` mean

The Ubuntu manual page for "ls" neither explains what the "author" is and it also does not mention that the option only applies to long format. From a GNU/Hurd man page:

--author List each file's author when producing long format directory listings. In GNU/Hurd, file authors can differ from their owners, but in other operating systems the two are the same.

Example:

ls -l --author
total 0
lrwxrwxrwx 1 rinzwind rinzwind rinzwind 20 2011-06-18 19:33 Desktop

will shows 3 names instead of 2 (owner, group, author).

I found some good information on this on an old mail archive for gnu from 2002 but in Ubuntu it is the same as the user name.

If you need to set 'author' the idea is you create a man page for your function and add an author tag in the man page. Unless you use something other than Ubuntu and actually can set this.

Ubuntu – ~/.bashrc return can only ‘return’ from a function or sourced script

It looks like you should "source" the script. That means running it like this:

. ~/.bashrc

It's effectively the same as typing all the command into the shell you are running it from and has the effect of changing the environment of the running shell (which doesn't happen if it's run as a sub-process).

Best Answer

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Ubuntu – What does `ls –author` mean

Ubuntu – ~/.bashrc return can only ‘return’ from a function or sourced script

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