Puppy Linux Discussion Forum

[Bruce B]

Chapter 63 - auto ext2|3 filesystem check and repair

The scripts in this post will automatically find, check and repair as needed your unmounted ext2 and ext3 partitions.

Script: autofsck

[Bruce B]

Chapter 64 - the important filesystem checks

The pup_save file. That's where your operating system is, (for frugal users). It's the file you really want to keep free of errors. It's also the file most susceptible to errors.

A primary obstacle is; we can only safely check and repair filesystems when they are not mounted. The pup_save file gets mounted early in the boot process.

Moreover, over the last several releases, Barry has implemented various techniques for dealing with this. Considering the changes, I can't come up with a one solution.

Version 4.00 did the e2fsck automatically, people complained it was taking too long.

On newer versions, I've noted a variable which can be set puppy pfix=fsck

From the way I read the forum, most people are probably using a version with this variable. From that standpoint, maybe there isn't even a problem to solve.

I have no desire or intention of running Puppy or any Linux on filesystems with errors, so, if I were the admin over Puppy computers, I'd put the pfix=fsck line in GRUB.

The other partition of importance is the pup_save host partition. I modified my init to remove all checking of the pup_save file and set it to check the host and the pup_save file before anything of consequence occurs. Code excerpt to follow:

[Bruce B]

Chapter 65 - assuring only one instance is running

I prepare these posts with Puppy's excellent outliner 'notecase'. Notecase allows multiple instances of itself. It also allows multiple instances of the same file.

To make things easy, I have a shell script called tui to open notecase with tui.ncd also loaded. Problem is notecase can open more than one tui.ncd and I can damage a document by editing a document open elsewhere.

I wish to demonstrate in this chapter how we can be assured we only have one instance of file open, using conditional checking and branching.

Remember how we can uses grep's exit code to verify conditions? We'll do it again here.

[Bruce B]

Chapter 66 acd (means auto change directories)

The code in this chapter is unique, you might have to pay very careful attention.

First

I want you to be able to easily open .bashrc, edit it and source it. Here is the command I want you to copy and paste:

alias ea='mp /root/.bashrc ; source /root/.bashrc'

Notes: if you don't like mp, use another editor. Also, when using spaces in your .bashrc file always use ' after the = and ' at the end of line.

ea means 'edit alias'

Second

Copy and paste this command to .bashrc;

alias rf='source /root/.bashrc'

This will easily re-source an existing instance of bash. Suppose you have five instances open and change one. The other four need sourced again.

Third

Remember, we can change directories with aliases. I can type usrbin faster and easier than I can type cd /usr/bin.

I now give you a script which will add change directory aliases from the command line, without the need to open .bashrc and edit it. I call the script acd for auto change directories

To use, simply type acd + the name of the shortcut you want- when you are in the directory you want to add a shortcut to.

Example: when in /root/.mozilla, you can type acd .mozilla and your shortcut is added. You no longer need to type cd /root/.mozilla. Just type .mozilla Then use 'rf' to activate it in the current shell. Otherwise, it will activate next time you open it.

Forth

Using colors: I gave you colors to work with, this is the first script where I added colors. If you didn't install colors, then you must change the cecho to echo. If the colors are not to your liking you need to modify them

Lastly, here is the script;

[Bruce B]

Chapter 67 - easy note taking

As a part of our computing tasks, we often want to jot down a few notes. With the GUI, this might involve opening a text editor, making our notes, saving changes and closing.

This task can be made much easier with a simple script, considering command line users often have the emulator open at all times.

For purpose of this chapter we will call our script note.

[Bruce B]

Chapter 68 - (ComeOn Dialog!)

I suppose any shell programmer will want to know 'dialog'. I've used it a couple times, in this series. This is your first lesson on dialog. We'll be using its 'menu' feature in this chapter. Here is the code:

[Bruce B]

Chapter 69 - awk

I use awk in my scripts for printing and rearranging specified columns.

Suppose I want to keep an up to date hosts file to save the time of the DNS queries.

The utility host makes these DNS queries, but formats them wrong for use in the hosts file

host -4 example.com
prints;
example.com has address 208.77.188.166
the above formatted output won't work with the /etc/hosts file

host -4 example.com | awk '{ print $4" "$1 }'
prints;
208.77.188.166 example.com
this output is perfect for /etc/hosts

What I did to format it right was print column 4 first, then a space character, followed by column 1.

Keep in mind, awk is much more powerful than my simple example. (and potentially much more complex)

For some chapters on awk

Linux Shell Scripting Tutorial (LSST) v1.05r3
A Beginner's handbook - by Vivek G. Gite
http://www.freeos.com/guides/lsst/index.html

I've attached the file host, which isn't included in Puppy, so you can make your own DNS queries and test the lines in this chapter. Put it in your /root/bin directory. Don't confuse the name with hosts, they are two different files.

~

Chapter 69 - awk

[Bruce B]

Chapter 70 - piping to scripts

I'll call this script ucase

#!/bin/bash
tr [:lower:] [:upper:]
exit 0

I leave it to you to figure how to make lcase

This is the first time we've used an exit code in a script.

We've seen many examples of piping to binary files. This is the first time we've made a script for piping.

My main point is to demonstrate we can pipe to our scripts, if we build them for that purpose. And considering we might want a successful return code we add one.

It would be easier to say:

< infile ucase

than

< infile tr [:lower:] [:upper:]

But frankly, I think ucase and lcase are too seldom used to even bother with. However, I think it good to know about the utilities in your tool box. With tr, if we want to change case in our files or even filenames, it's fairly easy.

~

Chapter 70 - piping to scripts

[Bruce B]

Chapter 71 - updating dialog

My main purpose in this chapter is to make an exercise where you can practice updating an application if it needs updated. In other words: practice developing skills

While visiting the Dialog Web Site, I noticed my Puppy version of dialog was old. So I updated it.

To check your dialog version:

dialog --version
Version: 1.1-20080819 (my current one)

If yours is older and you want to accept the assignment of updating it, you can go to the Dialog home page, linked above. Then to the 'download the latest section'. The file you would want would be dialog_1.1-20080819-1_i386.deb

I think your training level should be such that you can install this Debian package using 'disrpm' and 'mc' without much explanation.

Listed below are the package contents, note; they all go in /usr. You may choose not to install foriegn locales.

Please note: Lots of documentation to reference and learn from. And you can place documentation in different directories or make convenient symlinks.

[Bruce B]

Chapter 72 - symlinks

If you did the exercise in Chapter 71, you now have many examples of how to use dialog.

These examples are in;
(file://)/usr/share/doc/dialog/examples

Note: when we have a directory 5 levels deep, we want easy ways to access that directory, if we plan to visit it often.

1) You could bookmark this directory in Midnight Commander; merely navigate to /usr/share/doc/dialog/examples, then ctrl / to add the bookmark

2) you could add an alias

-----------------------------

This chapter looks like a good place to discuss the ln command.

Suppose we want to access /usr/share/doc/dialog/examples as if it were a subdirectory in our doc directory /root/doc; here is how;

cd /root/doc
ln -s /usr/share/doc/dialog/examples

This will make what we call a 'symlink' called examples which points to /usr/share/doc/dialog/examples and acts as if we directly accessed /usr/share/doc/dialog/examples

Suppose we don't want the name examples because it is too ambiguous, and it is. Then a different command;

cd /root/doc
ln -s /usr/share/doc/dialog/examples dialog-examples

Says we want our symlink named - dialog-examples

(we choose the name)

~

Chapter 72 - symlinks

[Bruce B]

Chapter 73 - the dot

A chapter on the character period (.). Also known in the slang as the dot. (well, yes)

In many cases the punctuation character - period - has a variety of meanings. I won't say anything about the dot as a punctuation character because we all know it as such.

The dot as the current directory

rox . (opens rox in the current directory)
mc . (opens mc in the current directory)

./scriptname (runs the script in the current directory, even though it is not in the path)

Dot as the source command shorthand

. filename (is shorthand for the long command source)
source filename (being the same as the command above)

Utilities

find /usr | grep ".png" finds all files with the text string 'png' even if there is no dot

find /usr/bin | grep "\.png" finds all files with only the text string '.png'

Directories

Whereas . means the current directory, .. would mean the parent directory.

cd .. would take you back (up) one directory

cd ../.. would take up back (up) two directories

cd ../foo would take you back one and over to foo

Guess what rox .. , or mc .. would do?

Dot for hiding files

When a file name starts with a dot, such as .foo, it's called a hidden file. It is not really a hidden file, but it won't be displayed by many programs.

If you want to open the bookmarks file in /root/.mozilla/somewhere/ it might not show in leafpad. Worse, files in this directory might not show to Mozilla (SeaMonkey)

A SeaMonkey workaround could be a symlink

cd
ln -s .mozilla mozilla

Then you could access /root/.mozilla by way of /root/mozilla.

cp and mv commands

These require a source and destination. Again the dot applies as the current directory.

Example:

cp /root/foo .

The dot suffices as the destination and you don't need to type in the directory. cp understands . to mean the current directory

This is all for the chapter. If you find the punctuation mark 'period' is behaving differently that a mere printing character, it might be because it really is.

~

Chapter 73 - the dot

[Bruce B]

Chapter 74 - how to not auto start X

I've seen this question asked with some frequency. I'll show you how I boot to the command prompt without starting X

I edit /etc/profile and change the line below

from
exec xwin
to
# exec xwin

When using a Linux that uses run levels, I edit /etc/inittab to use run level 2 or 3

~

Chapter 74 - how to not auto start X

[Bruce B]

Chapter 75 - a colorful calendar

Puppy comes with an useful utility called cal. I won't say much about it except, familiarize yourself with it.

I'm attaching to this post a similar utility which has been around for ages called ccal. Apart from displaying a colored calendar, it has the ability to keep appointments, birthdays, dates and other items for you.

I'm working and have about completed a script to make data entry for this utility very easy. A day or three maybe?

This is version 3.5 and I think a slightly newer version is available from at least the Debian repositories. But in reading the release notes, I didn't see a particular advantage to it.

Enjoy!

~

Chapter 75 - a colorful calendar

[Bruce B]

Chapter 76 - conditional checks and branches

Writing programs for yourself is different than writing for distribution. You already know many of the conditions on your computer. You don't necessarily know all you need to know on your client's computer. For this reason, you may want to check some conditions prior to running the meat of your script. This of course especially applies if damage can be done.

Example 1 - do we have all dependent files?

Sometimes the successful operation of our script requires other files. Here is an example of how to check for dependent files:

[Bruce B]

Chapter 77 - Links browser

For this chapter, I'd like you, if you are following the course, to download and install a curses browser. Ultimately, I think we'll have two or three browsers, but currently I'd like you to install 'links' from Puppy's official server.

links-2.1pre30.pet in the pet packages 4 directory ( there is an earlier version in the 3 directory, so make sure you get it from the 4 directory )

links differs from other ncurses browsers in that it also has a graphics mode which when running X can be enabled with the -g switch.

You could make a script called xlinks to save extra typing.