Handy wallpaper for basic linux commands
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Posts tagged ‘Basics’
Getting started with awk
This qref is written for a semi-knowledgable UNIX user who has just come up against a problem and has been advised to use awk to solve it. Perhaps one of the examples can be quickly modified for immediate use.
Basics of iptables
Alot of people are freaked out by IPTables and find it hard to understand. However, once you get the grasp of it the basics are easy. This document will serve as a basic how-to on using iptables.
Stdin, stdout and stderr
There are three types of standard streams for Unix-like operating systems. Standard streams are preconnected input and output channels between a computer program and its environment (typically a text terminal) when it begins execution. The three I/O connections are called standard input, standard output and standard error.
From Wikipedia:
Standard input (stdin)
Standard input is data (often text) going into a program. The program requests data transfers by use of the read operation. Not all programs require input. For example, the dir or ls program (which displays file names contained in a directory) performs its operation without any stream data input. Unless redirected, input is expected from the text terminal which started the program.
Standard output (stdout)
Standard output is the stream where a program writes its output data. The program requests data transfer with the write operation. Not all programs generate output. For example the file rename command (variously called mv, move, ren) is silent on success.
Standard error (stderr)
Standard error is another output stream typically used by programs to output error messages or diagnostics. It is a stream independent of standard output and can be redirected separately. The usual destination is the text terminal which started the program to provide the best chance of being seen even if standard output is redirected (so not readily observed). For example, output of a program in a pipeline is redirected to input of the next program, but errors from each program still go directly to the text terminal.
It is acceptable—and normal—for standard output and standard error to be directed to the same destination, such as the text terminal. Messages appear in the same order as the program writes them, unless buffering is involved. (For example, a common situation is when the standard error stream is unbuffered but the standard output stream is line-buffered; in this case, text written to standard error later may appear on the terminal earlier, if the standard output stream’s buffer is not yet full.)
Linux file permissions
The basics of file ownership and permissions on Linux. Learn to understand who are the owners of a file or directory, how the file permissions work and how you can view them, and learn how to set basic file permissions yourself.
Linux File Structure Cheat Sheet
In this session we are going to cover the basics of the linux file structure. I’ve attached an image I stumbled across on the net some time ago, as well as an explanation about each directory. Note the following file is distro independent. Enjoy.
Guide for tar, gzip, and bzip2
Another issue I see on the message boards quite frequently users are trying to get their heads around tar archiving utilities, and gzip/bzip2 compression utilities. It pays to keep in mind that in the Windows world both of these are packaged together in the .zip format. In the Linux world, as with most things, more control comes at the price of more complexity, as the two issues of archiving and compression are separated.
I guess the first thing we should do is discuss the difference. Compression is a means to shrink the physical size of a file in bytes. The technical aspects of how compression works is a bit beyond the scope of this guide, so suffice it to say that the computer uses an algorithm to combine redundant bytes of data together. Archiving on the other hand, is the act of combining several files together into one, for ease of backup and distribution, all the while keeping the individual file attributes and permissions intact.
Expanding on cp, mv, and rm commands
In this entry we’re going to look at a few of the options for the copy, move and remove commands. Enjoy.
An Introduction to Linux Command Line Absolute Basics
Be sure to review the commands below and feel free to give them a try on your system. You can download this blog as a PDF for further review here.
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