Question: Can you explain how to use OR, AND and NOT operators in Unix grep command with some examples?
Answer: In grep, we have options equivalent to OR
and NOT operators. There is no grep AND opearator. But, you can simulate
AND using patterns. The examples mentioned below will help you to
understand how to use OR, AND and NOT in Linux grep command.
The following employee.txt file is used in the following examples.
$ 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
You already knew that grep is extremely powerful based on these
grep command examples.
Grep OR Operator
Use any one of the following 4 methods for grep OR. I prefer method number 3 mentioned below for grep OR operator.
1. Grep OR Using \|
If you use the grep command without any option, you need to use \| to separate multiple patterns for the or condition.
grep 'pattern1\|pattern2' filename
For example, grep either Tech or Sales from the employee.txt file.
Without the back slash in front of the pipe, the following will not
work.
$ 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. Grep OR Using -E
grep -E option is for extended regexp. If you use the grep command
with -E option, you just need to use | to separate multiple patterns for
the or condition.
grep -E 'pattern1|pattern2' filename
For example, grep either Tech or Sales from the employee.txt file. Just use the | to separate multiple OR patterns.
$ 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. Grep OR Using egrep
egrep is exactly same as ‘grep -E’. So, use egrep (without any option) and separate multiple patterns for the or condition.
egrep 'pattern1|pattern2' filename
For example, grep either Tech or Sales from the employee.txt file. Just use the | to separate multiple OR patterns.
$ 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. Grep OR Using grep -e
Using grep -e option you can pass only one parameter. Use multiple -e
option in a single command to use multiple patterns for the or
condition.
grep -e pattern1 -e pattern2 filename
For example, grep either Tech or Sales from the employee.txt file.
Use multiple -e option with grep for the multiple OR patterns.
$ 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
5. Grep AND using -E ‘pattern1.*pattern2′
There is no AND operator in grep. But, you can simulate AND using grep -E option.
grep -E 'pattern1.*pattern2' filename
grep -E 'pattern1.*pattern2|pattern2.*pattern1' filename
The following example will grep all the lines that contain both “Dev” and “Tech” in it (in the same order).
$ grep -E 'Dev.*Tech' employee.txt
200 Jason Developer Technology $5,500
The following example will grep all the lines that contain both “Manager” and “Sales” in it (in any order).
$ grep -E 'Manager.*Sales|Sales.*Manager' employee.txt
Note: Using
regular expressions in grep is very powerful if you know how to use it effectively.
6. Grep AND using Multiple grep command
You can also use multiple grep command separated by pipe to simulate AND scenario.
grep -E 'pattern1' filename | grep -E 'pattern2'
The following example will grep all the lines that contain both “Manager” and “Sales” in the same line.
$ grep Manager employee.txt | grep Sales
100 Thomas Manager Sales $5,000
500 Randy Manager Sales $6,000
Grep NOT
7. Grep NOT using grep -v
Using grep -v you can simulate the NOT conditions. -v option is for
invert match. i.e It matches all the lines except the given pattern.
grep -v 'pattern1' filename
For example, display all the lines except those that contains the keyword “Sales”.
$ grep -v Sales employee.txt
200 Jason Developer Technology $5,500
300 Raj Sysadmin Technology $7,000
400 Nisha Manager Marketing $9,500
You can also combine NOT with other operator to get some powerful combinations.
For example, the following will display either Manager or Developer (bot ignore Sales).
$ egrep 'Manager|Developer' employee.txt | grep -v Sales
200 Jason Developer Technology $5,500
400 Nisha Manager Marketing $9,500
