regular expression HowTo - Linux / Unix Q & A from nixCraft

Nginx Redirect URL With HTTP/1.1 301 Moved Permanently Header

last updated July 15, 2011 in Nginx

How do I redirect old ugly urls such as http://example.com/store/view.jsp?product=foo with clean url – http://example.com/store/view/product/foo using nginx reverse proxy?

WordPress Rename Image URL For a CDN Usage

last updated November 21, 2010 in Apache, Lighttpd, Nginx, PHP

Recently, we moved all our static assets to a CDN as described here. However, we have over 8000+ old blog posts and we need to point static images url to our CDN account hosted at http://MyACCOUNT.cloudfront.net/images/ folder. How do I rename all image urls stored in wordpress posts? How do I offload static images to a CDN urls under Wordpress?

Regular expressions in grep ( regex ) with examples

last updated May 6, 2020 in BASH Shell, Linux, UNIX

How do I use the grep command with regular expressions on a Linux and Unix-like operating systems? How do I use grep and regular expressions (regex)to search for text/ words in Linux?

Search Multiple Words / String Pattern Using grep Command on Bash shell

last updated May 14, 2020 in BASH Shell, Debian / Ubuntu, FreeBSD, Linux, RedHat and Friends, Suse, UNIX

How do I search multiple strings or words using the grep command? For example I’d like to search word1, word2, word3 and so on within /path/to/file. How do I force grep to search multiple words? How can I grep for multiple patterns on Linux, OS X, FreeBSD, or Unix-like system? What is the command to search multiple words in Linux?

sed: Remove All Digits / Input From Input

last updated December 22, 2008 in AIX, BASH Shell, CentOS, Debian / Ubuntu, Fedora Linux, FreeBSD, HP-UX Unix, Linux, OpenBSD, Solaris-Unix, Suse, Uncategorized, UNIX

Q. How do I remove all digits or number from my text file or input using sed command?

Lighttpd as you compiled without pcre support error and solution

last updated November 19, 2007 in CentOS, Lighttpd, Package Management, RedHat and Friends, Troubleshooting

Q. I’m using lighttpd under CentOS 5 and getting the following error:
…can’t handle ‘$HTTP[url] =~ …’ as you compiled without pcre support.

My question is What is pcre support, and how do I solve this problem?

A. Pcre is nothing but Perl-compatible regular expression library. PCRE has its own native API, but a set of “wrapper” functions that are based on
the POSIX API are also supplied in the library libpcreposix. You must compile lighttpd with pcre to support lighttpd regex style config option. pcre-devel package provides the development files (Headers, libraries for static linking, etc) for pcre. Install the following package and rebuild your lighttpd:
# yum install glib2-devel openssl-devel pcre-devel bzip2-devel gzip-devel

Now change directory to lighttpd source code and recompile Lighttpd with pcre option:
# make clean # ./configure # make # make install

Now restart lighttpd and it should support pcre style config options.

sed: Remove All Except Digits (Numbers) From Input

last updated August 19, 2009 in BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, RedHat and Friends, Suse, Ubuntu Linux, UNIX

How do I remove all (text, special characters, white spaces, tabs etc) from my text file (input) except numbers (digits) using sed command?