Ubuntu – Modify the “alert” alias in ~/.bashrc

bashcommand linenotification

System: Lubuntu 14.04 LTS

I want to know if it's possible to modify the alert alias provided in ~/.bashrc in a particular way. This is the original alert:

# Add an "alert" alias for long running commands.  Use like so:
#   sleep 10; alert
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'

Use of default alias “alert” explains what it does.

And here is an example of the default notification on my system (using xfce4-notify) when I run ls; alert which, of course, completes successfully:

If I run a nonsensical command, asdfgh; alert, I see this:

The terminal icon has been replaced with the error icon because of

-i "$([ $? = 0 ] && echo terminal || echo error)"

As of now, the notification has just two items:
– the icon which is terminal or error depending on the success of the "previous" command
– the command itself (ls in the first case and asdfgh in the second)

I can modify the existing alias to include a line of text above the command like this:

alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "Task finished" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'

Then, if I run ls; alert and asdfgh; alert I get the notifications shown below.

My question is this: Both notifications show "Task finished" but can the same logic that is used to decide whether the terminal icon or the error icon is shown be applied again to determine which text string is shown above the command? So, if the terminal icon displays, the text would be "Task finished" but if the error icon displays, the text could something like "Something went wrong!"

Best Answer

Tl;dr

Use this:

alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && (echo terminal; exit 0) || (echo error; exit 1))" "$([ $? = 0 ] && echo Task finished || echo Something went wrong!)" "$(history | sed -n "\$s/^\s*[0-9]\+\s*\(.*\)[;&|]\s*alert\$/\1/p")"'

Simply evaluating $? again won't work, because by the time $? would be evaluated the second time it would contain the first command subsitution's ($([ $? = 0 ] && echo terminal || echo error)'s) exit status (always 0 since the two echos would always succed). A trick to go around this would be making the first command substitution exit with an equivalent exit status again:

$([ $? = 0 ] && (echo terminal; exit 0) || (echo error; exit 1))

This way $? could be evaluated a second time in order to decide which string to print:

alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && (echo terminal; exit 0) || (echo error; exit 1))" "$([ $? = 0 ] && echo Task finished || echo Something went wrong!)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]+\s*//;s/[;&|]\s*alert$//'\'')"'

On another note your history|tail -n1|sed -e '\''s/^\s*[0-9]+\s*//;s/[;&|]\s*alert$//'\'' is a bit over-convoluted. This would be way more readable:

history | sed -n "\$s/^\s*[0-9]\+\s*\(.*\)[;&|]\s*alert\$/\1/p"

So, final command:

alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && (echo terminal; exit 0) || (echo error; exit 1))" "$([ $? = 0 ] && echo Task finished || echo Something went wrong!)" "$(history | sed -n "\$s/^\s*[0-9]\+\s*\(.*\)[;&|]\s*alert\$/\1/p")"'

You can test by running (exit 0); alert and (exit 1); alert.

Related Solutions

Ubuntu – How to force a new Notification in notify-osd to show up without waiting for the earlier one to exit

There is a patch for this bug at - https://bugs.launchpad.net/ubuntu/+source/libnotify/+bug/257135?comments=all

@izx has made a ppa version for the patch so installation is now easy (thank you izx!)- How do I use 'notify-send' to immediately replace an existing notification?

To install, open a terminal and:

sudo apt-add-repository ppa:izx/askubuntu
sudo apt-get update
sudo apt-get install libnotify-bin

Now you should have installed a patched version of notify-send that can now replace and print id numbers, so you can use just one notification box for your shell script. The program now has -p and -r options, or the long syntax being --print-id and --replace-id

I wrote up a script based on your original that will make use of this, the starting and stopping notifications display until the stopped and started display, and it reuses the same notification box, if you have installed the patched version, make an file called config.txt and put the number 0 inside, then put that file in the same folder as your lampp.sh file.

#!/bin/sh

SERVICE='proftpd'

if ps ax | grep -v grep | grep $SERVICE > /dev/null

then
notify-send -t 0 -p -r `cat config.txt` -i /opt/lampp/htdocs/xampp/img/logo-small.gif "Stopping XAMPP ..." >config.txt && gksudo /opt/lampp/lampp stop && notify-send -r `cat config.txt` -t 5000 -i /opt/lampp/htdocs/xampp/img/logo-small.gif "XAMPP Stoped."  
else
notify-send -t 0 -p -r `cat config.txt` -i /opt/lampp/htdocs/xampp/img/logo-small.gif "Starting XAMPP ..." >config.txt && gksudo /opt/lampp/lampp start && notify-send -r `cat config.txt` -t 5000 -i /opt/lampp/htdocs/xampp/img/logo-small.gif "XAMPP Started."

fi

Edit This is how it shows on mine... enter image description here

Ubuntu – Use of default alias “alert”

You could use the man pages to get details about what the commands combined here do. Here's a little about the purpose of those commands here:

"$([ $? = 0 ] && echo terminal || echo error)"

This would echo terminal or error as per to the execution status - successful or fail respectively of the last command; and the result is as the value to the -i switch of notify-send for displaying the icons.

history|tail -n1

..to get the last command executed.

and sed to parse the text to display it with notify-send message.

To understand these try the following:

true; echo "$([ $? = 0 ] && echo terminal || echo error)"

..this would echo terminal.

false; echo "$([ $? = 0 ] && echo terminal || echo error)"

..this would echo error.

notify-send -i terminal 'Please note the icon..' 'the default icon for the terminal has been used. You can specify any other icon of your choice'

And,

echo $?

..is very useful to know the exit value of the last command executed.

echo "$(echo "the output of this command enclosed within \$(...)") is being supplied here in the outer echo command where is used as an argument."

..nested echo as a simple demo for using $() in a command combo.

Best Answer

Tl;dr

Related Solutions

Ubuntu – How to force a new Notification in notify-osd to show up without waiting for the earlier one to exit

Ubuntu – Use of default alias “alert”

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