brief introduction

In grep, we have options equivalent to OR and NOT operators, but no AND operators. However, we can use patterns to simulate AND. The examples in this article will help to understand how to use OR, AND and NOT operations of grep commands for text search.

This article will use the following employee.txt file as an example to illustrate:

$ cat employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
400  Nisha   Manager    Marketing   $9,500
500  Randy   Manager    Sales       $6,000

Grep OR operator

The grep OR function can be implemented using the four methods provided below.

1. Use "\"

If you use the grep command without any options, you need to use "\" to separate multiple modes of conditional OR.

grep 'pattern1\|pattern2' filename

For example, grep comes from Tech or Sales in the employee.txt file. If there is no backslash before the separator |, the following operation is invalid.

[jinguang1@localhost ~]$ grep "Tech|Sales" employee.txt
[jinguang1@localhost ~]$ grep "Tech\|Sales" employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
500  Randy   Manager    Sales       $6,000

2. Use the - E option

The grep-E option is used to extend regular expressions. If you use the grep command with the - E option, you only need to use | as the conditional OR to separate multiple modes.

grep -E 'pattern1|pattern2' filename

For example, grep comes from Tech or Sales in the employee.txt file. Use only "|" as multiple patterns.

[jinguang1@localhost ~]$ grep -E "Tech|Sales" employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
500  Randy   Manager    Sales       $6,000

3. Use egrep

The functions of egrep and grep-E are identical.

egrep 'pattern1|pattern2' filename

For example, grep comes from Tech or Sales in the employee.txt file. Use only "|" as multiple patterns.

[jinguang1@localhost ~]$ egrep  "Tech|Sales" employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
500  Randy   Manager    Sales       $6,000

4. Use grep-e

With the grep-e option, you can only use one parameter. If you want to use multiple modes, you need to provide multiple - e options in the command.

grep -e pattern1 -e pattern2 filename

For example, grep comes from Tech or Sales in the employee.txt file. Use multiple - e options to support multiple OR modes.

[jinguang1@localhost ~]$ grep -e Tech -e Sales employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
500  Randy   Manager    Sales       $6,000

Grep AND

1. Use - E "pattern1.*pattern2"

There is no AND operator in grep, but you can use the - E option to simulate it.

grep -E 'pattern1.*pattern2' filename
grep -E 'pattern1.*pattern2|pattern2.*pattern1' filename

The following example will grep all rows containing "Dev" and "Tech" at the same time, and keep the corresponding sequence containing strings.

[jinguang1@localhost ~]$ grep -E "Dev.*Tech" employee.txt
200  Jason   Developer  Technology  $5,500

The following example will grep all rows containing "Manager" and "Sales" and the string can appear in any order.

[jinguang1@localhost ~]$ grep -E "Manager.*Sales|Sales.*Manager" employee.txt
100  Thomas  Manager    Sales       $5,000
500  Randy   Manager    Sales       $6,000

2. Use multiple grep commands

You can use pipes to connect multiple grep commands to simulate the AND operator.

grep -E 'pattern1' filename | grep -E 'pattern2'

The following example will grep all rows containing "Manager" and "Sales" and the string can appear in any order.

[jinguang1@localhost ~]$ grep Manager employee.txt | grep Sales
100  Thomas  Manager    Sales       $5,000
500  Randy   Manager    Sales       $6,000

Grep NOT

Using the grep-v option, you can simulate the NOT operator. The - V option is designed to match all rows that do not contain the specified pattern.

grep -v 'pattern1' filename

The following example shows all rows that do not contain the "Sales" keyword.

[jinguang1@localhost ~]$ grep -v Sales employee.txt
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
400  Nisha   Manager    Marketing   $9,500

The following example shows all Manager s and Developer s, but ignores Sales.

[jinguang1@localhost ~]$ grep -E "Manager|Developer" employee.txt | grep -v Sales
200  Jason   Developer  Technology  $5,500
400  Nisha   Manager    Marketing   $9,500