Ubuntu – ny command-line software to create e-books from the scratch in Ubuntu

Short Version:

• Find the Exec command for your app by grepping the applications directory

  grep 'Calculator' /usr/share/applications/*
  

• Start the app

  gcalctool
  

• Kill it by hitting Ctrl+C

First, find out where your application is. A few directories are in an environment variable $PATH, so that you don't have to type the whole directory.

One way to find your app is to open the Menu Editor (right click on the Applications Menu and select Edit Menus) and find the app's command.

The calculator, for example is gcalctool at /usr/bin/gcalctool (use the whereis command to find the exact path of an app). Since /usr/bin is in the PATH variable (type echo $PATH), you can run it in your terminal by typing gcalctool.

It's now running in the foreground. You can pause it by pressing Ctrl+Z, resume it in the background by typing bg,or resume it in the foreground by typing fg. You can also use fg to raise an app to the foreground.

If you do this with multiple apps, you can use jobs to get a numbered list of all of them, and then use, for example, fg 3 to raise one of them.

An App that is in the foreground can be killed with Ctrl+C or Ctrl+\ (if it doesn't react to the former).

A universal way to find your app is to open the File Browser, go to Filesystem → usr → share → applications and to find your app there.

You'll see a bunch of .desktop files, which you can drag into a Text Editor (or use cat) to read. This is a piece of the Calculators .desktop file:

[Desktop Entry]
Name=Calculator
Comment=Perform arithmetic, scientific or financial calculations
Exec=gcalctool

The Exec entry is what you're interested in here. It's the same you would see if you went to the Menu Editor, just quicker. You can grep the files to search them for your app, if you can't find it.

If the app doesn't have a .desktop file in the applications directory, you have to know it's command of course. Use TAB to get suggestions from just a few letters. Press tab, tab, y to get a huge list of every application.

Even a simpler script to toggle between activating or deactivating a particular ppa. Save the code given below in a file, for instance toggle_ppa.sh.

#!/bin/bash
#
# toggle_ppa.sh
#
# created by souravc (https://askubuntu.com/users/127327/)
# modified by Glutanimate (https://askubuntu.com/users/81372/)
#
# originally released at https://askubuntu.com/q/383605/81372
#
# DESCRIPTION:  Detects if a PPA is active/inactive and deactivates/activates it
#               on user confirmation.
#
# USAGE:        toggle_ppa.sh ppa:launchpaduser/ppaname

### VARIABLES

SOURCEDIRECTORY=/etc/apt/sources.list.d
PPA="$1"

### USAGE CHECKS

## Arguments

if [ -z "$PPA" ]
then
    echo "Error: Please provide a PPA name to toggle between activation/deactivation"
    echo "The PPA name should be formatted as it appears on launchpad, e.g.:
"$0" ppa:webupd8team/y-ppa-manager"
    exit 1
fi

## Root privileges

if [ "$(whoami)" != "root" ]; then
  echo "Error: This script needs root privileges. Restarting..."
  sudo "$0" "$1"
  exit
fi

### MAIN

SOURCELIST_NOPFX="${PPA#*:}" #remove 'ppa:' prefix
SOURCELIST="${SOURCELIST_NOPFX////-}"-$(lsb_release -cs) #replace all slashes with dashes, include release
SOURCEFILE="$SOURCEDIRECTORY"/"$SOURCELIST".list #compose sources list path

if [ -e "$SOURCEFILE" ]
then
    echo "Processing $SOURCEFILE..."
    SOURCE_COMMENTED=$(grep "^\#deb\ " "$SOURCEFILE") #check if sources line is commented
    if [ -z "$SOURCE_COMMENTED" ]
    then
        echo "$PPA is active. Going to deactivate. Proceed? [ y/n ]"
        read ANSWER
        if [ $ANSWER == "y" ]
        then
            sed -i "s/^deb\-src/\#deb\-src/" $SOURCEFILE
            sed -i "s/^deb\ http/\#deb\ http/" $SOURCEFILE
            echo "Updating package index files..."
            sudo apt-get update
            echo "Done."
        else
            echo "Aborted."
            exit 0
        fi
    else
        echo "$PPA is inactive. Going to activate. Proceed? [ y/n ]"
        read ANSWER
        if [ $ANSWER == "y" ]
        then
            sed -i "s/^\#deb\-src/deb\-src/" $SOURCEFILE
            sed -i "s/^\#deb\ http/deb\ http/" $SOURCEFILE
            echo "Updating package index files..."
            sudo apt-get update
            echo "Done."
        else
            echo "Aborted."
            exit 0
        fi
    fi
else
    echo "Error: Source file at $SOURCEFILE for $PPA does not exist. Please check PPA name."
    exit 0
fi

Follow the procedure given at the other answer to keep file in PATH and make it executable.

Usage

sudo toggle_ppa.sh <full-ppa-name>

Example

sudo toggle_ppa.sh ppa:webupd8team/java

How it works

The working principle of this code is the same as in my other answer. The code acts in a very interactive manner. When someone runs this along with ppa name as its argument, it will display the PPA's current status and what the code is going to do on successful execution. Then it will ask permission of the user. Only if the user inputs 'y' to confirm the code will change the status of the PPA and activate/deactivate it. It will immediately abort if the user puts an 'n' for no.