Software developers are often required to work with large datasets or files, such as CSVs or logs.

Rather than loading the entire data into memory, developers can filter out, narrow down, and transform output to only focus on relevant lines or sections, such as specific logs, function calls, errors, and so on.

Filtering output based on patterns

The grep command — which stands for global regular expression print — is used to filter the lines of any given input based on patterns:

$ grep [-i] [-v] pattern [file ...]

Where:

• -i is an optional flag used to make grep case insensitive.

• -v is an optional flag used to invert the search.

• pattern is a string literal or a basic regular expression to find.

• file ... is a list of file paths to read the content from.