Tim's questions

In light of https://unix.stackexchange.com/a/254854/674 and https://unix.stackexchange.com/questions/458895/how-can-i-bring-a-background-gui-job-to-the-front-of-my-desktop, there is an example from manpage of xdotool

# Activate google-chrome when you move the mouse to the bottom-left corner: 
xdotool behave_screen_edge bottom-left search --class google-chrome windowactivate

The manpage says

--class Match against the window class.

--classname Match against the window classname.

What are "class" and "classname"?

What possible values do they have?

How can I find out the class and classname of a window?

Thanks.

My host OS is Ubuntu 14.04 and guest OS in VirtualBox is Windows 8.1. I can switch from host to guest by Alt+Tab, but can't from guest to host by the same method which only switches between windows in guest OS. How can I switch from guest to host? Thanks!

Btw, I still would like a way to switch between windows in guest OS.

Accidently, I entered full-screen display in the terminal. I now can't get out of the full screen display back to normal display.

How can I do this?

How shall I find out the frequency and type of my current RAM? My OS is Ubuntu 12.04.

In Emacs run in terminal, ctrl+space is a standard shortcut key to select region. But under Ubuntu 12.04, it will invoke some input method for non-English language. I was wondering if I can reserve it for Emacs only?

Under System Settings -> Keyboard -> Shortcuts, I couldn't find to what ctrl+space has been bound. Strange.

Other programs, especially auto-complete in Eclipse, also seem to have a problem handling ctrl+space.

I have a scanned PDF file which is an application form, and a picture which is the scanned version of my signature (for example, this one) and can be in any image format such as EPS or PNG. I would like to put the signature picture on the blank space right to "APPLICANT:" on the second page of the application form. I wonder how to do that?

I have tried the following methods, but none succeeded:

1. The first way is using gimp. I first import the application form into gimp, and then paste the signature picture on the space right to "APPLICANT:" on the second page of the application form.

   The problems are that:

   • It seems that I can only import one page of the application form into gimp, not all of the two pages.

   • Also when I save the modification, the closest format to PDF I can save to is PS, and the resolution has been downgraded and the storage size of the saved file is 10 times bigger than the original application form and the signature picture.

2. The second way is using Libreoffice Draw. I have installed the libreoffice-pdfimport package. But after I import the application form into Libreoffice Draw,

   • all the scanned content is not imported, and

   • the layout is different from the layout of the original application form.

So what other ways can I try? I would prefer some way that can lay the signature picture directly on the application form PDF file,

• without having to convert between formats,
• without having to create much bigger files while keeping the original resolution,
• without having to split and combine pages of a multi-page pdf file,
• without having to rasterize other parts of the PDF file, i.e. without losing the text that I added later to the application form PDF file by having to convert the whole PDF into images.

I wonder how to create fillable forms in a PDF, such as this one. I would like to fill out the places that are required to fill out.

Possible Duplicate:
What should I do when Ubuntu freezes?

My OS is Ubuntu 12.04. Sometimes the screen suddenly becomes frozen, except that the mouse can move around. I have no choice but to hit the power button of my laptop.

In Windows, whenever screen becomes frozen, I just hit Ctrl+Alt+Delete to invoke task manager, which is still responsive, and kill the processes that consumes most resources and are likely the culprit of the freezing.

But in Ubuntu, I don't know what some good way to deal with such a situation.

Thanks!

How to check if a LaTeX package has been installed in Ubuntu?

When installing, I followed the methods mentioned in math.arizona.edu and n.wikibooks.org.

I was wondering if there are shortcuts for selecting some text in terminal, just similar to holding shift and type arrow key in editing a text file in a text editor. Thanks!

I try to unzip a zip file, but got an error:

$ unzip COCR2_100.zip 
Archive:  COCR2_100.zip
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
note:  COCR2_100.zip may be a plain executable, not an archive
unzip:  cannot find zipfile directory in one of COCR2_100.zip or
        COCR2_100.zip.zip, and cannot find COCR2_100.zip.ZIP, period.

I googled but didn't find a solution. I was wondering why it is and how I should fix it? Thanks!

The zip file can be downloaded from COCR2_100. It is an application, and here is its website http://users.belgacom.net/chardic/cocr2.html.

My OS is 10.10.

I was wondering what is the default saving directory for Accessories > Take Screenshot?

I just took a screenshot and I am looking for where it is saved.

I was wondering how to get the information about a package in the terminal, before installation with apt install so that I can decide whether to install it, based on the description.

Thanks!

At some point, the filesystem on my digital audio player has become read-only. I cannot copy files into it or remove files on it.

Are there some possible reasons for the player's file system to change permissions in this way?

I tried using chmod:

$ sudo chmod a+rw SGTL\ MSCN/ 
chmod: changing permissions of `SGTL MSCN/': Read-only file system

SGTL MSCN is the mount point of the digital audio player.

What else can I try to make it writeable?

I was wondering how to restrict the search range of "locate" to some directory?

For example, how to find files/directories with string "math" in their names under some directory "/home/tim/science/"?

Thanks and regards!

I have these three files: 1.zip, 1.z01 and 1.z02. I would like to extract and join them into a single file, by right clicking 1.zip and selecting Extract Here. But then there comes an error:

7-Zip 9.04 beta  Copyright (c) 1999-2009 Igor Pavlov  2009-05-30
p7zip Version 9.04 (locale=en_US.utf8,Utf16=on,HugeFiles=on,2 CPUs)

Error: /home/tim/Desktop/1.zip:
Can not open file as archive

Errors: 1

I was wondering what the problem is and how I can solve it?

ADDED:

Is my usage of unzip -FF wrong? It seems not working:

$ unzip -FF 1.zip 
Archive:  1.zip
warning [1.zip]:  zipfile claims to be last disk of a multi-part archive;
  attempting to process anyway, assuming all parts have been concatenated
  together in order.  Expect "errors" and warnings...true multi-part support
  doesn't exist yet (coming soon).
file #1:  bad zipfile offset (local header sig):  0

2nd ADDED:

Still ain't right:

$ cat 1.z01 1.z02 1.zip > combined.zip && unzip -FF combined.zip
Archive:  combined.zip
warning [combined.zip]:  zipfile claims to be last disk of a multi-part archive;
  attempting to process anyway, assuming all parts have been concatenated
  together in order.  Expect "errors" and warnings...true multi-part support
  doesn't exist yet (coming soon).
warning [combined.zip]:  209829313 extra bytes at beginning or within zipfile
  (attempting to process anyway)
file #1:  bad zipfile offset (local header sig):  209829313
  (attempting to re-compensate)
 extracting: 1.wmv   bad CRC ee181eef  (should be f3c61875)

It generated 1.wmv, which can play well only until midway in GNOME MPlayer.

3rd ADDED:

Am I using 7z wrongly?

$ 7z e 1.z01

7-Zip 9.04 beta  Copyright (c) 1999-2009 Igor Pavlov  2009-05-30
p7zip Version 9.04 (locale=en_US.utf8,Utf16=on,HugeFiles=on,2 CPUs)

Processing archive: 1.z01

Error: Can not open file as archive

$ 7z e 1.zip

7-Zip 9.04 beta  Copyright (c) 1999-2009 Igor Pavlov  2009-05-30 
p7zip Version 9.04 (locale=en_US.utf8,Utf16=on,HugeFiles=on,2 CPUs)

Processing archive: 1.zip

Error: Can not open file as archive

As far as I know, both Wine and Mono are used to run Windows applications under Ubuntu.

So I was wondering

1. what their differences are? Are they both virtual machines? Or does each belong to some other category?
2. It is better When to use which for what kinds of Windows applications? For example, those applications that may or may not require .net Framework.
3. Do they depend on each other? Are they required to install together? Or does each work independently without existence of the other?

Thanks and regards!

When editing the Applications menu, I see for some applications their commands have %U such as gedit %U and gnome-mplayer %U, but others don't such as gcalctool.

I was wondering what %U means when calling a command, and when it is needed and when it is not? Thanks!

This is motivated from my previous question, where I followed a reply but did not make it work.

In 10.10, when opening a directory in Nautilus, I was wondering how to copy the current path?

My address bar, pictured here, is not copyable:

I am planning to upgrade from 8.10 to 10.04. But I am wondering whether there will be data loss during the upgrade.

For example:

• Will the applications that I have installed on 8.10 still be there after upgrade?

• Will the settings of application such as the bookmarks for Firefox and for Google Chrome be preserved?

• Will all the personal files under my home directory be preserved?

Is there anything else I need to know about upgrading?