Meta-Characters

RegEx uses heavily meta-characters in order to easily find patterns inside a file

[] Brackets

It allows to define a range of characters for find them in a file.

For the demonstration we are going to use a file named file.txt with this content:

1
hello
2
goodbye

Finding alphabetic characters

$ grep "[a-z]" file.txt
hello
goodbye

Finding numbers

$ grep "[0-9]" file.txt
1
2

^ Negate

Finding no-alphabetic characters

$ grep "[^a-z]" file.txt
1
2

Finding no numbers

$ grep "[^0-9]" file.txt
hello
goodbye

Searching Text Starting and Ending With

For the sake of simplicity let’s change the content of the file by:

FirstName
LastName
Name1
1stName

^[ Starting With

Finding text starting with a number

$ grep "^[0-9]" file.txt
1stName

$ Ending With

Finding text ending in a number

$ grep "[0-9]$" file.txt
Name1

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