There are a number of reserved characters called metacharacters that do not represent themselves in a regular expression, but they have a special meaning that is used to build complex patterns. For example, the regexp pattern 1 matches the string “1”, and the pattern boy matches the string “boy”.

In a regular expression, most characters - including letters and numbers - represent themselves. Technically speaking, the word or phrase patterns are regular expressions-just very simple ones. A regular expression - or “regexp”- is a text string of special characters that specifies a set of patterns to match. In addition to word and phrase searches, you can use grep to search for complex text patterns called regular expressions. NOTE: These regexps were quoted with characters this is because some shells otherwise treat the “ˆ”character as a special “metacharacter.” To output lines in the file “book” that contain a “$” character, type: The following samples describe some regexp examples for commonly searched-for patterns. Many examples discussed in this article have practical implications meaning you can use them in your daily Linux programming. In this article, we show you to run advance string searching using Grep with regular expression by giving you 10 hands-on examples on its implementations. Eventually, the grep command was written to do this search on a file when not using ed. The name “grep” derives from a command in the now-obsolete Unix ed line editor tool - the ed command for searching globally through a file for a regular expression and then printing those lines was g/re/p, where re was the regular expression you would use. The grep Linux/Unix command line utility is one of most popular tools for searching and finding strings in a text file.

He is also a senior instructor and developer living in Washington DC.

He is a senior editor at Touchstone Words where he writes and reviews coding and technology articles. He has written extensively on advanced topics on web design, mobile app development and blockchain. Matt Zand is the founder of High School Technology Services, DC Web Makers and Coding Bootcamps.

Linux search files for text string not