Ubuntu – How to get [TAB] to work with arguments of aliases to autocomplete as can be done with the actual command

aliasbashcommand line

I have many aliases that I created in my .bash_aliases file, and they are very useful, so if I want all info on a package I do something like:

allinfo software-center

And that does the equivalent of:

apt-cache show software-center

As the alias is set as:

alias allinfo='apt-cache show'

But there is one disadvantage of this, I am currently unable to autocomplete with TAB when using allinfo instead of the actual command. So I was wondering if there was a way to overcome this disadvantage and make it so that doing allinfo software-ce[TAB] will work just the same as it does when you use it with the actual command, and not just make a large tab space?

I am using gnome-terminal.

OS Information:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 15.04
Release:    15.04
Codename:   vivid

Package Information:

gnome-terminal:
  Installed: 3.14.2-0ubuntu3
  Candidate: 3.14.2-0ubuntu3
  Version table:
 *** 3.14.2-0ubuntu3 0
        500 http://gb.archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages
        100 /var/lib/dpkg/status

Best Answer

Great question! If your allinfo command was the same as just apt-cache, (ie, without the show) then we could look at the completion for apt-cache, and apply that to your allinfo alias.

However, you want a subset of the apt-cache completion, so we have a little more work to do.

If we look in the completion definition for apt-cache - in /usr/share/bash-completion/completions/apt-cache, we see the following is used for the show subcommand:

        COMPREPLY=( $( apt-cache --no-generate pkgnames "$cur" 2> /dev/null ) )

- this is just setting the COMPREPLY variable to the list of matching packages.

So, we can borrow this and write our own function, and bind it to your allinfo alias:

# define a function to print the possible completions for
# an allinfo invocation
_allinfo()
{
    _init_completion || return
    COMPREPLY=($(apt-cache --no-generate pkgnames "$cur" 2>/dev/null))
    return 0
}

# bind the above completion function to the 'allinfo' alias
complete -F _allinfo allinfo

If you add that fragement to your .bashrc file, you should get the completions working as you expect.

Related Solutions

Ubuntu – How to you mirror an autocomplete function in your own aliases (in 14.04)

Newer bash completion releases (>=2.0) improved hugely the time used to load the autocompletion logic. They made them by loading on request the required files, the newer location for these files is:

/usr/share/bash-completion/completions/

If you use ls -lah to explore such directory you'll find than there exist many soft links. That's because a file is needed for every command/alias, so, if you have pssh, pscp and prdp you'll need to create links with those names:

sudo ln -s /usr/share/bash-completion/completions/ssh /usr/share/bash-completion/completions/psss
sudo ln -s /usr/share/bash-completion/completions/ssh /usr/share/bash-completion/completions/pscp
sudo ln -s /usr/share/bash-completion/completions/ssh /usr/share/bash-completion/completions/prdp

Another alternative is to syslink the ssh autocompletion file to /etc/bash_completion.d/

sudo ln -s /usr/share/bash-completion/completions/ssh /etc/bash_completion.d/ssh

The former method will load the _ssh function on every single bash interactive session (making slower the startup).

After using any of the above methods your complete -F _ssh pssh ... configuration will relate the _ssh function with your aliases.

Ubuntu – pass arguments to an alias command

Aliases don't take arguments. With an alias like alias foo='bar $1', the $1 will be expanded by the shell to the shell's first argument (which is likely nothing) when the alias is run.

So: Use functions, instead.

d () {
  num=${1:-5}
  dmesg |grep -iw usb|tail -$num
}

num=${1:-5} uses the first argument, with a default value of 5 if it isn't provided.

Then you can do:

$ d
# prints 5 lines
$ d 10
# prints 10 lines

Or, if you change the options you used slightly:

alias d="dmesg|grep -iw usb|tail -n 5"

Then you can pass additional -n options:

$ d
# prints 5 lines
$ d -n 10
# prints 10 lines

If multiple -n options are specified for tail, only the last is used.

Best Answer

Related Solutions

Ubuntu – How to you mirror an autocomplete function in your own aliases (in 14.04)

Ubuntu – pass arguments to an alias command

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