Puppy Linux Discussion Forum

[Bruce B]

Shell Expansion

an alias is written like this:

alias myname='echo Bruce'

If I type myname, it will say Bruce on the console.

If I write the alias below I don't need the apostrophe

alias cls=clear

The reason why I don't need an apostrophe is because there are no
spaces in the alias.

Spaces are command delimiters. If we don't tell bash that our
command string with spaces is to be treated as a whole, it will treat
it as individual instructions each time it encounters a space and
bomb out.

I want to demonstrate variable expansion.

1) echo '$PATH'

2) echo "$PATH"

3) echo $PATH

You can select the command, the click you mouse wheel into the
console to save typing.

~

[Bruce B]

Keeping File Names Clean

My theory is many FOSS authors actually try and make Linux
friendly to Windows users. Many Linux utilities and programs now
work on 'dirty' Windows file names. Years ago, many Linux apps
would bomb out on bad file names.

Which ones and how many? I don't know. Knowing would be a
discovery process.

What I do is I clean up dirty filenames, so they will work with any
Linux utility or program and make our scripting easier.

Here is what I consider dirty filename for Linux

Elton John - I Don't Wanna Go On With You Like That.mp3

Here is the cleaned filename

Elton_John_-_I_Dont_Wanna_Go_On_With_You_Like_That.mp3

The worst part of the filename was the apostrophe in the word Don't

I think you will find the 'cleaned' file as easy to read as the 'dirty'
one.

If I keep my filenames 'clean'. I don't have to worry about what a
script will do when it processes them.

About six years ago I donated a script, one I didn't write, to Puppy.
It's name is spacereplace. Barry still includes it.
Use it to replace spaces with underscores.

For fine editing, the utility 'ytree' has been the best one I've found,
for ease of use.

Hint: Open it in the directory you want to work in. Hit enter to bring
all the files into a more full window. The rest is intuitive.

Compiling is straight forward

./configure
make install


Don't use the one hosted on Puppy's archive, something is wrong.
Also, it might be an older version.

Get it here

http://www.han.de/~werner/ytree.html

~

[jpeps]

[Bruce B]

[Bruce B]

Making Life Easier

Our Linux system may contain 2 or 3 thousand executable files in our
path statement.

I don't remember the names of all the files.

I might be able to remember part of the name. If I remember the first
letters, tab completion can help me.

Otherwise?

Well these files are stored in numerous bin and sbin directories, and it is
a lot of work finding them by reading all the filenames in these directories.

Here is my idea of a helpful script

[Bruce B]

Linux is a Unix clone.

The authors working on Linux tended not to make too many utilities not
included in Unix.

ls is the Linux equivalent of the MS dir command.

I liked the dir command. If I wanted to see all the directories and only
directories, I could type 'dir /ad'

With ls or find it is not so easy, yet we can make scripts to add utilities
which don't exist.

I want, for example, to be able to:

* view all non-hidden directories
* nicely formatted
* in dictionary order
* and have an intuitive filename for my script

I can do this, it takes a few minutes to write the script, from then on I
have the script for my Linux systems. This is why I keep my scripts in
their own directories, it is easy for me to retrieve my scripts to new Linux
installs.

My intuitive filename is: ad (that was the switch used in the dir
command and it means to me 'all directories', (only my script doesn't
show the hidden ones, on purpose)

Next I'll explain the commands

find . -type d -maxdepth 1

. is our current directory
-type d means display the type directory - not files
-maxdepth 1 means I don't want to see any subdirectories

grep -v '^\./\.'

grep -v , the -v switch means display everything that does not match my
criteria

'\./\.' is my criteria, using the find command the beginning of hidden
directories, looks like this ./. , if I want grep to look for literal periods, I
have to escape them. Remember our common escape character is the \ ,
the ' ' are used to tell grep the beginning and end of our criteria and don't
allow for any shell expansion

cut -d "/" -f 2

The cut command can be used to remove output, the find command will
output a directory like this; ./foobar , we want it to display only foobar,
the cut command uses / as the delimiter,
like this -d "/" and the -f switch says print only text after field 1

sort -d will sort our text, the -d switch says to do it in dictionary order.
Linux is case sensitive and we want to display like this:

mydocuments
MyFiles

Which would be a non case sensitive sort

grep -v '^\.$' will eliminate a line which only has a period

^ means start of line
$ means end of line
\ escapes the period

We pipe to filter output, the pipe symbol is | , the output from the
command on the left, becomes the input for the command on the right.
When done, the filtered output is displayed on screen.

Now, the parts of the script have been explained, we can put them
together.

[jpeps]

[Bruce B]

[Bruce B]

jpreps,

I don't see a problem with your logic, so I modified it and attached a modified file.

admodified

Bruce

Note: I found one switch improvement, changed sort -d option to sort -f

[Bruce B]

CLI variables AKA arguments AKA parameters AKA ???

We've seen plenty of examples of variables in our scripts.

This brief post will serve as a primer to introduce you to the command
line variables.

I use the for loop. The for loop has not been explained YET. But I will.

Life is easier because I now have an official editor - jpreps

If I goof, or boo-boo, I get free help. This is one of the advantages on
FOSS development - peer review.

[PupGeek]

Bruce, I am not too clear on why you placed the three echo statements a few posts back. I tried them each and noticed that while the $PATH and "$PATH" were treated as variables, the '$PATH' was treated as a literal. Are what's contained in single quotes always treated as a literal in echo statements?

Oh, and would you be able to make a thread all about regular expressions? That stuff just throws me way off, and I haven't seen too much in the docs about it, but it can probably be very useful to me if I knew better how to use it.

[Bruce B]

[puppyluvr]

Hello,
OK, so how do I get this whole thread as a text file...

OK, really, probably a noob question, but if I write scripts using alias`s on my system, they will not run on other systems???

[Bruce B]

[Bruce B]