What Is GREP in Linux and How Do You Use It?

Grep is a Linux / Unix command-line tool used to search for a string of characters in a specified file. The text search pattern is called a regular expression. When it finds a match, it prints the line with the result. The grep command is handy when searching through large log files.

1. What is grep used for?
2. How do I use grep to find words?
3. How do I grep a file in Linux?
4. What does grep mean?
5. Why is grep so fast?
6. What does AWK do in Linux?
7. How do I search for something in Linux?
8. How do you grep special characters?
9. How do I use grep to find a file?
10. How do I grep two words in Linux?
11. How do you open a file in Linux?
12. How do you grep a word in Linux?

What is grep used for?

grep is a command-line utility for searching plain-text data sets for lines that match a regular expression. Its name comes from the ed command g/re/p (globally search for a regular expression and print matching lines), which has the same effect.

How do I use grep to find words?

The easiest of the two commands is to use grep's -w option. This will find only lines that contain your target word as a complete word. Run the command "grep -w hub" against your target file and you will only see lines that contain the word "hub" as a complete word.

How do I grep a file in Linux?

How to use the grep command in Linux

1. Grep Command Syntax: grep [options] PATTERN [FILE…] ...
2. Examples of using 'grep'
3. grep foo /file/name. Searches the file /file/name for the word 'foo'. ...
4. grep -i “foo” /file/name. ...
5. grep 'error 123' /file/name. ...
6. grep -r “192.168.1.5” /etc/ ...
7. grep -w “foo” /file/name. ...
8. egrep -w 'word1|word2' /file/name.

What does grep mean?

grep Global regular expression print. The grep command comes from the command used by the ed program (a simple and venerable Unix text editor) to print all lines matching a certain pattern: g/re/p.

Why is grep so fast?

GNU grep is fast because it AVOIDS LOOKING AT EVERY INPUT BYTE. GNU grep is fast because it EXECUTES VERY FEW INSTRUCTIONS FOR EACH BYTE that it does look at. ... GNU grep uses raw Unix input system calls and avoids copying data after reading it. Moreover, GNU grep AVOIDS BREAKING THE INPUT INTO LINES.

What does AWK do in Linux?

Awk is a utility that enables a programmer to write tiny but effective programs in the form of statements that define text patterns that are to be searched for in each line of a document and the action that is to be taken when a match is found within a line. Awk is mostly used for pattern scanning and processing.

How do I search for something in Linux?

Basic Examples

1. find . - name thisfile.txt. If you need to know how to find a file in Linux called thisfile. ...
2. find /home -name *.jpg. Look for all . jpg files in the /home and directories below it.
3. find . - type f -empty. Look for an empty file inside the current directory.
4. find /home -user randomperson-mtime 6 -iname ".db"

How do you grep special characters?

To match a character that is special to grep –E, put a backslash ( \ ) in front of the character. It is usually simpler to use grep –F when you don't need special pattern matching.

How do I use grep to find a file?

The grep command searches through the file, looking for matches to the pattern specified. To use it type grep , then the pattern we're searching for and finally the name of the file (or files) we're searching in. The output is the three lines in the file that contain the letters 'not'.

How do I grep two words in Linux?

How do I grep for multiple patterns?

1. Use single quotes in the pattern: grep 'pattern*' file1 file2.
2. Next use extended regular expressions: egrep 'pattern1|pattern2' *. py.
3. Finally, try on older Unix shells/oses: grep -e pattern1 -e pattern2 *. pl.
4. Another option to grep two strings: grep 'word1\|word2' input.

How do you open a file in Linux?

There are various ways to open a file in a Linux system.
...
Open File in Linux

1. Open the file using cat command.
2. Open the file using less command.
3. Open the file using more command.
4. Open the file using nl command.
5. Open the file using gnome-open command.
6. Open the file using head command.
7. Open the file using tail command.

How do you grep a word in Linux?

Search any line that contains the word in filename on Linux: grep 'word' filename. Perform a case-insensitive search for the word 'bar' in Linux and Unix: grep -i 'bar' file1. Look for all files in the current directory and in all of its subdirectories in Linux for the word 'httpd' grep -R 'httpd' .