Tracking User's activity using "script -a"

Unix System provides a very good method allows us to capture of all commands issued by the user “XYZ”. For this, we can user "script" command. This will print all what appears on the screen (commands and their output) to the filename

But remember, Its not a User History.... It stores all commands entered by all users (.e. its the shell history .

Add the following line to your BASH profile

script -a ~/.termlog`date +%m%d%y`

This enable to capture all the terminal activities to a file ending with current date

Cut and paste text files by columns

How many times have you wanted to edit those results files columnwise?

Here’s a generic UNIX way: (startcol and endcol refer to character columns, including whitespace. Tab counts as 1.)

cut -cstartcol-endcol file {>receiving file} paste sourcefile1 sourcefile2 {>final file}

I like to preview and fine-tune my commands by looking at the result on standard out (the shell window) and then redirecting output to a (temporary) file when things look right. Those feeling really adventurous can combine things into a single command line…

Great Unix Tips & Tricks: Vol 1

Whether you are a newbie to Linux or you are a seasoned guru, you are bound to find some scripts or programs which just make your life on the computer exponentially easier. The following is a list of them and explains what they do.

1. tac

tac is a command similar to cat, except that it reverses the output of the specified file.

tac

2. Multiple X-Sessions

Using multiple X-Sessions allows a user to have open more than just one instance of XFree, so multiple desktop environments can be used at a time.

startx -- :

terminal name is simply which terminal X should start on. By default it starts on

0:0. If you want two open, you may want it open on 0:1, which can be run by:

startx -- :1

The resulting desktops will exist on F7 - F12.

3. links

links is a text based browser which has full support for tables

links

is simply the hostname or IP address of the computer to connect to.

sparse files

Due to the Unix concept of sparse files, you can create seemingly enormous files that in reality take next to no disk space. The following program will create a 305,419,897 byte file called 'core' that may result in you receiving a 'cleanup' email message from a less-than-seasoned Unix sysadmin even though it occupies virtually no real disk space.

    $ cat bigcore.c
    #include 
    #include 

    int main(void) {
        int fd = open("core", O_CREAT|O_WRONLY|O_TRUNC, 0600);
        lseek(fd, 0x12345678, SEEK_SET);
        write(fd, "1", 1);
        close(fd);
        return 0;
    }

    $ cc -o bigcore bigcore.c
    $ ./bigcore
    $ ls -l core
    -rw-------  1 dmr  staff  305419897 May  1 03:50 core
    $ du -k core
    48      core
    $

Ctrl+D or exit: Which one is better?

In BASH, to exit from shell we can use Ctrl+D or exit ? which one is better?

-Ctrl+D conveniently exits Bash
-Sometimes too conveniently bcoz session may be terminated if pressed accidentaly.

To avoid the accidental exit, we can specify the no of "Ctrl+D" pressed before exit.

$export IGNOREEOF=1

$ Ctrl+D
$ Use "exit" to leave the shell.
$ Ctrl+D
$ exit

Games

If you like to use Linux and only Linux, and you also like to play games on your computer, the best choice is to buy native Linux games (games that run without any intermediate layer on your Linux system). You can find lots of information about available games and even order them through the links below.

Naturally there are also lots of free games, many simple but fun games are included with Linux distributions, but some are not, so I have included links about those too.

Linux Game Publishing
Tux Games
Linux Gaming
Linuxgames
The Linux Game
Mandrake eXPerience FREE GAMES section
Article on Gaming and Linux in 2003

Command based Calculator in BASH

Bash can perform simple arithmetic operations at the command prompt.

To use this feature, simply type in the arithmetic expression you wish to evaluate at the prompt within double parentheses, as illustrated below. Bash will attempt to perform the calculation and return the answer.


bash> echo $((16/2))
8

bash> echo $((16*2))
32