GREP USAGE IN LINUX CODE
GREP USAGE IN LINUX WINDOWS

-before-context (or -B) displays a specified number of lines before your match.-after-context (or -A) displays a specified number of lines after your match.There’s a trio of options for doing this, and they’re as easy to remember as A-B-C (literally):

For example: $ grep -only-matching -line-number Fedora example.txtĪ common way to get context about how-or why-a pattern appears in a file is to view the line above the match, or the line just after it, or both. For added context, use the -line-number option ( -n for short) to see the line number where the matched pattern appears in the file. The -only-matching (or -o for short) grep option prints only the matching part of a line. If your text file has extra long lines, then your results can contain a lot more data than you anticipate since grep doesn’t lift the string out of context. Yet, you can use a command such as strings to extract just the binary file’s plain text, and then use grep on the results like this: $ strings example.xcf | grep gimpĪ line of text is considered a string of characters terminating with a new line character-specifically, 0x0D0A or , the carriage return (CR) and line feed (LF) ASCII characters respectively. For instance, you can’t normally grep through a binary file, since binary files don’t contain much raw text. This tactic also enables grep to be used in situations when it otherwise might not be effective. For example, this command searches for iana only in the last 10 lines of 's source code, instead of searching the whole page: $ curl | tail | grep iana One is helping to narrow grep's scope by searching through only the results of another process. Here’s an example: $ grep BSD example.txtĪnother common way to use grep is with a pipe, making it a sort of filter. The canonical use of grep is searching for a precise string of characters in some greater body of text, and returning the line or lines containing successful matches.

GREP USAGE IN LINUX WINDOWS

GNU grep is available from OpenCSW.Īnd finally, you can get grep and many more commands on Windows by installing the open source Cygwin package, which provides a vast collection of GNU and open source tools. Solaris: Ships with the Sun version of grep, which can differ from GNU’s and BSD’s versions.GNU grep is available from your Illumos distribution’s repository. Illumos: Some distributions ship with the Sun version of grep, which can differ from GNU’s and BSD’s versions.BSD (and systems primarily using BSD tools): Ships with the BSD version of grep, but GNU grep is available in the ports tree.This article pertains specifically to GNU grep, the default grep on Linux systems, but here’s some information in case you’re using another member of the UNIX family. Though, this fact can also be confusing: While most grep commands attempt to be interchangeable with one another, not all grep commands are exactly the same. This situation is convenient because it means that no matter what UNIX or UNIX-like system you use, you have a grep command available.

GREP USAGE IN LINUX CODE

Since then, the grep command’s code has been written and rewritten by several different programmers, but its name has persisted. (This tool received wide release only because Thompson's department head, Doug McIlroy, asked for a tool “to look for stuff” in files.) The grep command, which is an initialism for global regular expression print, started its life as a personal utility script on the computer of the co-creator of UNIX, Ken Thompson. If you are a sysadmin or programmer and find yourself obsessively dipping into streams of text on a POSIX system, then you have probably either encountered grep, or come across a time you wished you could use this command. Most people would be disappointed to learn that sysadmins and code monkeys more often poke at streams of text in hopes of getting the right response. Their goal? To reach into the virtual reality of the Internet, gathering the binary forces of code into the applications and infrastructure we all use today. Most people imagine that system administrators and programmers fiddle with knobs and diodes.

Grep usage in linux