echo the alias command before running it

Question

I've got a few aliases I want to clarify. They are working. How can I make this an option for many other aliases. Awk or grep? And pointers helpful. Thanks.

# IP addresses
alias myip="echo  '# myip  curl https://ipecho.net/plain; echo #'; curl -sS https://ipecho.net/plain; echo"
alias hazip="echo '# hazip curl https://ipv4.icanhazip.com     #'; curl -sS https://ipv4.icanhazip.com"
alias ips='myip && hazip'

 ~ ips
# myip  curl https://ipecho.net/plain; echo #
1.2.3.4
# hazip curl https://ipv4.icanhazip.com     #
1.2.3.4

Answer 1

Example ~/.bash_aliases file:

alias hi=" echo Hello"

You can modify this content to the following, to solve your problem:

alias hi=" type hi; echo Hello"

Output in case 1:

$ hi
Hello

Output in case 2:

$ hi
hi is aliased to `type hi; echo Hello'
Hello

Answer 2

How about something like this:

shopt -s extdebug
shopt -u expand_aliases

function check_for_alias {
    COMMAND=$(alias $BASH_COMMAND 2> /dev/null)
    if [ $? -eq 0 ]
    then
        tput setaf 1
            echo $COMMAND
        tput sgr0        
        ${BASH_ALIASES[$BASH_COMMAND]}
        return 1
    fi
}

trap check_for_alias DEBUG

Explanation:

I use so called bash DEBUG trap to call a function before any command. Inside I can use $BASH_COMMAND variable to view what is currently being called:

function check_for_alias {
    echo $BASH_COMMAND
}
trap check_for_alias DEBUG

This won't do for aliases because in the handler they are already expanded - I have to disable their expanding, and then call them manually:

shopt -u expand_aliases

function check_for_alias {
    # ...
    ${BASH_ALIASES[$BASH_COMMAND]}
}

Unfortunately, bash still tries to run an unexpanded alias, so I reveive an error telling me that command is not found. To bypass this I enable debugging and return 1 from handler if I detect that the command I run is an alias

shopt -s extdebug

function check_for_alias {
    COMMAND=$(alias $BASH_COMMAND 2> /dev/null)
    if [ $? -eq 0 ]
    then
        # ...
        return 1
    fi
}

Finally to print alias I use tput to use red font. Output command is stored in $COMMAND variable.

tput setaf 1
    echo $COMMAND
tput sgr0  

Answer 3

First of all, I need to stress on the fact, that there is no ready solution to echo alias command before execution. At least, I couldn't find anything like that... But it doesn't mean, that we can't leverage bash flexibility to come up with whatever we want!

The solution below consists of a couple of parts, but there is nothing hard to implement on any Ubuntu system:

1. Create a dedicated file in your home folder or any other folder, suitable for you. Let it be ~/.aliases

2. The contents of this file must be something like this:

als() {
  alias_name="$1"
  cmd="$2"
  alias $alias_name="echo ; echo $cmd ; echo && $cmd"
}

als gl "git log"
als glns "git log --name-status"
als sshc-router "ssh [email protected]"

To understand, how it works, let's take a look at the first command: als gl "git log" This is a regular call for bash function, that accepts two parameters: gl is alias name and "git log" is alias command.

The contents of als() function are quite straitforward: it just builds echoed output for each passed command. For the command above, the final alias will look like the following:

alias gl="echo ; echo git log ; echo && git log"

(Empty echo's required to add more new lines for the command to see it better.)

As you can see, the way of adding new alias commands is even simpler, than original command structure alias name=command.

3. After you created a file and added all the needed aliases to it, all you have to do is to add the following to your ~/.bashrc file:

ALIAS_FILE=$HOME/.aliases
if [ -f "$ALIAS_FILE" ]; then
    source "$ALIAS_FILE"
fi

This ~/.bashrc file is called every time on terminal opening. Consequently, this aliases will be available in your console without any additional activities from your side! Nice and neat!

4. And the last step. Let's just open the console and test out our solution:

user@user-pc:~/work/projects/your-project$ gl

git log

commit 543c1d070c0b52a510def7ec8a451472c513019c (HEAD -> feature/FEATURE-999-branch)
Author: John Doe 
Date:   Tue Jan 24 18:01:14 2023 +0100