grep Ignore Case in Linux

1. the grep Syntax in Linux
2. the grep Case Sensitivity in Linux
3. the grep Case Insensitive With the -i Option

In this tutorial, we will learn to use grep documentation to ignore cases in filenames. But first, let’s start with grep.

Each file is searched for patterns using grep. Patterns list patterns separated by newlines, and grep outputs each line that matches a pattern.

Patterns should usually be quoted when using grep in a shell command. Recursive searches check the working directory if no file is specified, while non-recursive searches read standard input.

the grep Syntax in Linux

The syntax for the grep command is given below:

$ grep [OPTIONS] PATTERN [FILE...]

Optional items are shown within square brackets.

• The OPTIONS - grep has several settings that can be used to customize how it behaves.
• The PATTERN is a pattern you can use to find something.
• The FILE is the name of one or more input files.

The user who runs the command must have read access to the file to search.

the grep Case Sensitivity in Linux

The grep command’s default behavior is case-sensitive. Case-sensitive accepts lowercase letters that differ from uppercase letters.

For example, the pattern THANOS does not match thanos, Thanos, or ThanoS. The text file looks like this:

$ grep "THANOS" thanos.txt

Output:

THANOS

the grep Case Insensitive With the -i Option

The grep command’s -i option can perform a case-insensitive search. For a case-insensitive search, the search pattern THANOS matches Thanos, ThaNos, or ThanoS.

$ grep -i "THANOS" thanos.txt

Output:

THANOS
thanos
Thanos
ThanoS

The ignore-case option is a more extended variant of the -i option. As a result, we can use the grep command with the ignore-case option for a case-insensitive match.