Pandya's questions

From Community Help > Repositories, Software in Ubuntu’s repository is divided into four categories or components: main, restricted, universe and multiverse.

• Main: The main component contains applications that are free software, can be freely redistributed and are fully supported by the Ubuntu team.
• Universe: The universe component is a snapshot of the free, open-source, and Linux world. It houses almost every piece of open-source software, all built from a range of public sources.
• Restricted: Proprietary drivers that make it possible to install Ubuntu and its free applications on everyday hardware
• Multiverse: The multiverse component contains software that is not free, which means the licensing requirements of this software do not meet the Ubuntu main component licence policy.

We can understand why restricted components are provided. As the page says,

Our commitment is to only promote free software – or software available under a free licence. However, we make exceptions for a small set of tools and drivers that make it possible to install Ubuntu and its free applications on everyday hardware. These proprietary drivers are kept in the restricted component. Please note that it may not be possible to provide complete support for this software because we are unable to fix the software ourselves - we can only forward problem reports to the actual authors. Some software from restricted will be installed on Ubuntu CDs but is clearly separated to ensure that it is easy to remove. We will only use non-open-source software when there is no other way to install Ubuntu. The Ubuntu team works with vendors to accelerate the open-sourcing of their software to ensure that as much software as possible is available under a free licence.

However, why is the multiverse category included? What is the purpose of it?

There is wide range of non-free/proprietary applications & software included in the multiverse category. I don’t understand why this is considered a good thing.

I am using Xubuntu 14.04 (Ubuntu + xubuntu-desktop), The following Message shown many times (such as executing mousepad , zenity etc).

$ mousepad
Gtk-Message: Failed to load module "overlay-scrollbar"
pandya@pandya-desktop:~$ zenity --info
Gtk-Message: Failed to load module "overlay-scrollbar"

Why I am getting this message? How to solve?

Many new users make mistakes (or have misunderstanding) while applying chmod on files or directories, because of a lack of informative knowledge of:

• Symbolic notation for ugo and rwx
• Use of octal numbers

So, in this answer I have provided some useful information that can help to understand correct symbolic notation and using octal numbers.

I want to display:

1. All users and

2. All groups

   in my system using command-line.

users and groups commands display users currently logged in, and groups a user belongs to respectively.

How to display a list of all users and all groups by command-line?

We know bash supports number of buitin commands like:

$ type type cd help command
type is a shell builtin
cd is a shell builtin
help is a shell builtin
command is a shell builtin

I want to get list of all available shell builtin commands. How do I do that by command-line?

Recently I found command: command which has no manual entry but help displays as follows:

$ help command
command: command [-pVv] command [arg ...]
    Execute a simple command or display information about commands.

    Runs COMMAND with ARGS suppressing  shell function lookup, or display
    information about the specified COMMANDs.  Can be used to invoke commands
    on disk when a function with the same name exists.

    Options:
      -p    use a default value for PATH that is guaranteed to find all of
        the standard utilities
      -v    print a description of COMMAND similar to the `type' builtin
      -V    print a more verbose description of each COMMAND

    Exit Status:
    Returns exit status of COMMAND, or failure if COMMAND is not found.

Is command -v is alternative of which?

What arguments are accepted by this command and how/when to use command?

How to get speech output from entered text by using command-line?

Also facility to change speech rate, pitch, volume etc using simple command.

I recently found the following gvfs commands :

gvfs-cat (1)         - Concatenate files
gvfs-copy (1)        - Copy files
gvfs-info (1)        - Show information about files
gvfs-ls (1)          - List files
gvfs-mime (1)        - Get or set mime handlers
gvfs-mkdir (1)       - Create directories
gvfs-monitor-dir (1) - Monitor directories for changes              
gvfs-monitor-file (1) - Monitor files for changes
gvfs-mount (1)       - Mounts the locations
gvfs-move (1)        - Copy files
gvfs-open (1)        - Open files with the default handler
gvfs-rename (1)      - Rename a file
gvfs-rm (1)          - Delete files
gvfs-save (1)        - Save standard input
gvfs-set-attribute (1) - Set file attributes
gvfs-trash (1)       - Move files or directories to the trash
gvfs-tree (1)        - List contents of directories in a tree-like format

Now, how do these differ by the common commands like cat, cp, mkdir, etc.

In other words what is the difference between the following commands respectively:

• cat and gvfs-cat
• cp and gvfs-copy
• mkdir and gvfs-mkdir etc. and so on.

or what for gvfs-* commands stands for?

How to randomly execute one command within specified list of command? Helpful for randomly choosing startup sound, wallpaper or executing commands.

In General, if I have commands for execution as follows then How do I get randomness:?

#!/bin/bash
<command_1>
<command_2>
<command_3>
.
.
.
<command_n>

Then I want to execute randomly only one command from above possibilities when script is run!

How to do that?

When the echo $LOGNAME and logname commands run normally, I get identical results from them:

pandya@pandya-desktop:~$ echo $LOGNAME
pandya
pandya@pandya-desktop:~$ logname
pandya

Is there any difference between them?

Suppose I have a script like this:

(The example depicts an rysnc use case)

#!/bin/bash
echo -n "Enter Source Directory:"
read srcdir
echo -n "Enter Destination Directory:"
read dstdir
rsync -av --delete "$srcdir" "$dstdir"

The idea here is to prompt the user to enter the "Source" and "Destination" directories for rsync to work with. As is, the user will have to manually enter /path/to/directory/ via the command-line.

Instead, I want to prompt the user to enter the paths through a GUI interface.

Something like this:

What commands can I use to prompt the user with a GUI selection window that returns the file path to the command-line?

How to run any command in another terminal window?

Example: I opened one terminal window and if I run command like apropos editor, then it run and out-puts on that window. But I want to run same command on another terminal window (new window) instead on present window from first terminal.

Further clarification:
I need suggest-command <command> that open new terminal window and run mentioned <command> in that (newly opened) window. (where suggest-command is example of suggestion of command.)

How to do that?

What does /etc/alternatives stand for? How and why is it used?

I found gnome-tex-editor in /usr/bin which is linked as follows:

/usr/bin/gnome-text-editor -> /etc/alternatives/gnome-text-editor
/etc/alternatives/gnome-text-editor -> /usr/bin/gedit

So gedit and gnome-text-editor seem to be the same thing.

So why are some commands (e.g.: gedit and gnome-text-editor) provided twice?

And what is the use of /etc/alternatives/ - how does it work?

To print current/present working directory environment variable $PWD and command pwd are available. So, What is difference in usage of both? or What should be chose for specific purpose?

For displaying message and print data there are two command available printf and echo.
Then how differently they used? Which is more preferable?

I want to do something like following:

#!/bin/bash
command1
<pause for 30 seconds>
command2
exit

How can I do it?

Where can (should) I put my (bash) script so that it can be used (forever) by terminal or by a direct command: Alt+F2?

I know there is /usr/bin and /sbin & /bindirectories but when should I use between them?

Where should I put my script?

Apt (Advanced Packaging Tool) has option to download only package by apt-get -d install [pkg-name]. I have also find apt-get download [pkg-name] to download packages.

Then what is the difference between --download-only (apt-get -d install)and download (apt-get download)?

And When should I use between them?

I have simple text file named "example".

Reading with terminal command: cat example

Output:

abc cdef ghi jk lmnopq rst uv wxyz

I want to convert (transform) into following form: (expected output from cat example)

abc
cdef
ghi
jk
lmnopq
rst
uv
wxyz

How can I do this via the command-line?

(This is only an example file, I want to convert word's position in vertical-column)

I have run following command accidentally

sudo chown [username] -hR /

Now sudo su getting error:

sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set

How to Solve This?