Puppy Linux Discussion Forum

[Bruce B]

[Bruce B]

lspet

With this lstool you can view the contents of your pet package.
Helpful especially, if you have to manually 'unpet'.

[Shep]

[Bruce B]

I wrote a little script which will not work. It will work and produce the output shown in the comments after certain characters have been escaped. The escape character is used to change the meaning of the character sent to the 'for loop' is the \ (backslash). The backslash is used to give a literal meaning to the character rather then how bash uses it.

For example: echo ~ displays /root and echo \~ displays ~

[Bruce B]

Bash errors

Bash gives an error "command not found"

Sometimes you run into some though ones. This one about takes the cake.

Cross my heart - I was confident I did everything right. I looked at the code over and over and could not find the reason for the command not found.

I didn't find it with the mp editor. I can't find anything wrong with cat.

My dog didn't eat my homework but I think she messed up my script. It happens when I leave tasty stuff on the table, she sometimes jumps up on the keyboard uses it as a launch pad to the table to steal my food.

Here is the problem: She pressed the space bar to move the text to column 154, then I guess entered these characters ~V~R

I don't know this for a fact, but I confronted her and she didn't deny it.

As stated bash finds them and says command not found.

Cat don't display them. With persistence I debugged it and even wrote my own poor man's cat utility called kitty. Kitty won't display this character string on the screen either.

Echo will.

How many times I thought bash was the culprit only to find it wasn't.

Anyone else had tough times trying to figure why things just will not work right sometimes?

Anyone else started thinking the problem is Bash, because you couldn't find the problem in your source?

~~~~

Change subject

Hoping Shep or another sed expert is still around, I have a question.

I want to reduce lines empty lines more than two to double lines.

The obvious approach is to me


sed -e 's/^$^$^$^$/^$^$/' -e 's/^$^$^$/^$^$/'

It works, but I've learned enough to know that a sed expert knows the best way to do it.

Shep, anyone?

~

[Shep]

[Bruce B]

Introducing the file command

In its most simple form we use this external command to help figure what kind of file we are working with with.

In my example, mplayer.dsl has an unknown extension. The Linux distro Damn Small Linux uses it. I want to know what it is. I use file to look at it and report back.

I say file mplayer.dsl

file says: mplayer.dsl: gzip compressed data, from Unix

To learn more I say: gzip -d mplayer.dsl

gzip says: mplayer.dsl: unknown suffix -- ignored

I then say: mv mplayer.dsl mplayer.dsl.gz

Then I say: gzip -d mplayer.dsl.gz

Gzip decompresses it and leaves me with mplayer.dsl

Then I say: file mplayer.dsl

file then says: mplayer.dsl: POSIX tar archive (GNU)

Now I know it is a tar archive

Then I say: tar xvf mplayer.ds

Sure enough it extracts.

To learn more say file --help, for more details consult the man page.

~

[Bruce B]

How to make a RAM Disk - step by step

1) Define RAM Disk size

Edit menu.lst and set the size of the disk on the kernel line

ramdisk_size=192000

This would configure to make a disk size of about 192 MB

The 192000 is 192000k but the k is not entered

2) Format the RAM Disk in the file /etc/rc.d/rc.local

mkfs.ext2 -m 0 /dev/ram6

the -m 0 says not to allocate space for the super user. It gives more space and the super user allocation is not needed.

3) Fstab

tell /etc/fstab about the RAM disk



Code:

/dev/ram6 /mnt/ram ext2 rw,noatime,noauto,shortname=mixed,errors=continue 0 0

4) mount RAM disk

Use ROX-Filer mouse options on /mnt/ram

or use the command line

mount /dev/ram6

or

mount /mnt/ram

You can unmount either on the command line or with ROX-Filer

Comments

You can of course use a different disk size, mount point and ram device.

In Puppy we have three basic places to put apps or commands for automatic run.

/etc/rc.d/rc.local
/etc/profile.local
/root/Startup

Here is a guide of what which to use in a variety of circumstances. Any graphics app needs to be put in /root/Startup

Non graphics apps or instructions you only want to run one time per session, put in /ect/rc.d/rc.local

/etc/profile.local is susceptible to being run more than once, something to consider when placing commands in this file

Many readers knew this already. But for those who didn't, now you know.

It is possible that /etc/profile.local doesn't exist. If not make it as a regular text file. It is not a shell script

I use the RAM disk when I have big files or need to batch process files. These files might get modified, converted, deleted, remodified, decoded or encoded, renamed and whatever. This could make for a lot of disk I/O for files that only live a few minutes. The RAM disk speeds things up and saves any disk wear and tear. I also compile in a RAM disk for the same benefits.

The RAM disk I present in this post is what I call - "A true formatted RAM disk"

There are other kinds of RAM disks which can be set up easier. My reason for the so-called true formatted RAM disk is ffmpeg won't write to the other formats.

Thanks

~

[Indy'spup]

Ok I got to ask because this is killing me...

Does the Prefix -- used often with a command/function have any specific meaning in bash? As I understand it after the function has run the -- will disable other options pertaining to that function to run and terminate the command cleanly.

ie: --version, or --help etc. etc.

[Bruce B]

[Shep]

[01micko]

Hi scripters

I knocked up a script the other day mainly so I could make sure i could list the correct dependencies of a package that I was building. Note the -f argument that checks the ro filesystem. Suggestions for improvement are most welcome.

[Bruce B]

01micko

Trivial comment, but potentially frustrating, if one doesn't know.

Sometimes executable files are packed with UPX, when they are, the file is a valid executable file with dependencies, problem is, ldd fails, producing a false negative.

(I think an English teacher would fail me on the sentence above)

You check with the file command and get an accurate output.

Not a criticism or suggestion. Just something to put in your toolkit of ever expanding knowledge, in the event you didn't already know about the behavior.

Bruce

~

[01micko]

yeah, I did actually know about that Bruce.. from you I think in one of these threads. Just didn't think of it..

I wonder if there is a way to decompress the upx'd binaries and be able to check them with ldd?

[amigo]

upx -d decompresses bins, but there is no guarantee that the md5sum of the file will be the same after decompressing and then re-compressing -unless it is done more than once. After doing it once, repeating the operation will not change the md5sum anymore.