Open Source Research and Development

Free and Open Source R&D Projects, Articles, and Reviews

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Global Regular Expression Print Tools (grep variants)

Overview The UNIX grep utility marked the birth of a global regular expression print (GREP) tools. Searching for patterns in text is important operation in a number of domains, including program comprehension and software maintenance, structured text databases, indexing file systems, and searching natural language texts. Such a wide range of uses inspired the development […]

Negation in regular expressions

How to search for lines that don’t contain a particular pattern is fairly easy in some programs, obscure in others, and almost impossible yet in others. That is, assuming your program of choice supports regular expressions. I review how to achieve this functionality in Perl, Vim, grep, and vi.

Why grep ‘foo|bar’ file doesn’t work?

The bar | has no special meaning in BRE (basic regular expressions). Use extended regular expressions (ERE) such as: grep -E ‘foo|bar’ file or egrep ‘foo|bar’ file In GNU grep, you can also force the spcial meaning of | by escaping it. E.g., grep ‘foo\|bar’ file

Is grep an acronym? Does it mean GNU Regular Expression P?

grep originated from ed command: g/re/p where re is a regular expression, g stands for globally, and p stands for print. So one could say grep is an acronym of “Global Regular Expression Print“.

HTTP Proxy Over SSH Connection Mini-Howto

What is HTTP Proxy? HTTP proxy is a method to connect to a website by through an intermediate “proxy” server. The way it works is that your browser sends the request for a web page to the proxy server. The proxy server then forwards the request to the website. The website sends the requested page […]

Book Review: “Stealing the Network: How to Own a Continent”

“Stealing the Network: How to Own a Continent” is an interesting technical hacker story. Even though the plot of the story is not very well connected, the authors develop the story using real technology to compromise computer networks, which makes you feel that this is not just a fiction and it might be actually happening […]

Book Review: “Essential System Administration”

All you need to know about managing Linux/UNIX/BSD. At first glance, this book seems like a typical O’Reilly book: a narrow title, rich in material, and is beneficial to a much wider audience than the title reveals. It covers a wide range of system administration subjects and goes way beyond just the essentials. Over the […]