Using local mail as notification tool

Post created at 2022-05-04 14:25

I used to run commands and develop into linux terminal, and have some scheduled tasks running in the background.

I need to be notified on terminal about some finished processes in a generic form, without depending GUI notifications.

By default, every cron job thats writes to console is sent to user local email. So, local email will be my notification messages repository.

Setup

I used this setup in Ubuntu, but it must works in any distro.

Adding current user to mail group

Bash

$ sudo adduser $USER mail
Adding user 'guionardo' to group 'mail' ...
Adding user guionardo to group mail
Done.

Install mailtools, postfix, and mutt

Bash

$ sudo apt install mailtools postfix mutt

Send test mail

Bash

$ echo "This is a test" | mail "--subject=Test email" $USER@localhost

Test new mail

Bash

$ mail
"/var/mail/guionardo": 1 message 1 new
>N   1 Guionardo Furlan   qua mai  4 17:41  14/464   Test email
? q
Held 1 message in /var/mail/guionardo

Ok, we have an e-mail into our inbox. Lets read with better tool.

Bash

$ mutt

Bash

q:Quit  d:Del  u:Undel  s:Save  m:Mail  r:Reply  g:Group  ?:Help
   1 O F mai 04 To guionardo@lo (   2) Test email



---Mutt: /var/mail/guionardo [Msgs:1 Old:1 0,6K]---(threads/date)----(all)---

Bash

i:Exit  -:PrevPg  <Space>:NextPg v:View Attachm.  d:Del  r:Reply  j:Next ?:He
Date: Wed,  4 May 2022 17:41:20 +0000 (UTC)
From: Guionardo Furlan <guionardo@furlan-server>
To: guionardo@localhost
Subject: Test email
X-Mailer: mail (GNU Mailutils 3.7)

This is a test

-O F- 1/1: Guionardo Furlan       Test email                         -- (all)

Setup for notifications

Add this content to your ~/.profile or equivalent file (.bashrc, .zshrc, etc):

Bash

MAIL_CHECK_TIME=0
mail_prompt() {
    local pwd='~'
    local MAIL_SECONDS_DIFF=$MAILCHECK

    local MAIL_ELAPSED_SECONDS=$((SECONDS - MAIL_CHECK_TIME))

    [ "$PWD" != "$HOME" ] && pwd=${PWD/#$HOME\//\~\/}

    printf "\033]0;%s@%s:%s\033\\%s" "${USER}" "${HOSTNAME%%.*}" "${pwd}"

    if [[ "$MAIL_CHECK_TIME" -eq "0" || "$MAIL_ELAPSED_SECONDS" -gt "$MAIL_SECONDS_DIFF" ]]; then
        local MAILX="$(mailx 2>/dev/null &)"
        UNREADEN_REGEX="\s([0-9]{1,4})\sn"
        [[ $MAILX =~ $UNREADEN_REGEX ]] && UNREADEN=$(echo "${BASH_REMATCH[1]}") || UNREADEN=0
        local COUNT=$((UNREADEN))
        local MESSAGE_TEXT="message"
        if [ "$COUNT" -gt "0" ]; then
            if [ "$COUNT" -gt "1" ]; then
                MESSAGE_TEXT="messages"
            fi
            echo "$COUNT unreaden $MESSAGE_TEXT. Run mutt"
        fi
        MAIL_CHECK_TIME=$SECONDS
    fi

}

if [[ $(which mailx) ]]; then
    PROMPT_COMMAND="mail_prompt"
fi

Close and reopen your terminal to load this configuration
Now, when you access the terminal, messages not readden will show a prompt:

Bash

1 unreaden message. Run mutt

In your custom scripts, you can send email to your local user and get notified.

Extra

In WSL/ubuntu, I got an error when installing postfix. Working in it.