How to use the command 'rg' (with examples)

Ripgrep (rg) is a recursive line-oriented search tool that aims to be a faster alternative to grep. It is designed to search for regular expressions in files and directories, providing more powerful search capabilities than the traditional grep command.

Use case 1: Recursively search the current directory for a regular expression

Code:

rg regular_expression

Motivation: This use case is helpful when you want to search for a specific pattern or string within all files in the current directory and its subdirectories. It is useful for tasks like finding instances of a particular function or variable in a codebase.

Explanation:

• rg is the command itself.
• regular_expression is the pattern or string you want to search for.

Example output:

file1.txt: This is the first line.
file2.txt: This is the second line.
file3.txt: This is the third line.

Use case 2: Search for regular expressions recursively in the current directory, including hidden files and files listed in .gitignore

Code:

rg --no-ignore --hidden regular_expression

Motivation: Sometimes you may want to search for a pattern within all files in the current directory, including hidden files and files that are ignored by Git. This command allows you to do that, providing a comprehensive search across all files.

Explanation:

• --no-ignore ensures that the command does not ignore any files listed in .gitignore.
• --hidden enables searching in hidden files and directories.

Example output:

file.txt: This is the line with the regular_expression.

Use case 3: Search for a regular expression only in a subset of directories

Code:

rg regular_expression set_of_subdirs

Motivation: In some cases, you may only want to search for a pattern within specific directories rather than the entire directory tree. This command allows you to limit the scope of the search to a subset of directories.

Explanation:

• set_of_subdirs is a whitespace-separated list of directories you want to search in.

Example output:

dir1/file1.txt: This is the line with the regular_expression.
dir2/file2.txt: This is another line with the regular_expression.

Use case 4: Search for a regular expression in files matching a glob (e.g. README.*)

Code:

rg regular_expression --glob glob

Motivation: When you only want to search for a pattern in files that match a particular pattern or glob, this command comes in handy. It allows you to narrow down the search to files that have filenames conforming to a specific pattern.

Explanation:

• --glob glob is used to provide the glob pattern for filtering files to search in.

Example output:

file1.txt: This is the line with the regular_expression.
file2.txt: This is another line with the regular_expression.

Use case 5: Search for filenames that match a regular expression

Code:

rg --files | rg regular_expression

Motivation: In some cases, you may want to search for file names that match a specific pattern. This can be useful for tasks like finding all files with a particular extension or identifiable naming convention.

Explanation:

• --files lists all file names in the current directory and its subdirectories.
• The | (pipe) operator sends the output of the first command as input to the second command.
• rg regular_expression searches for the given regular expression in the list of file names.

Example output:

file.txt
file.md

Use case 6: Only list matched files (useful when piping to other commands)

Code:

rg --files-with-matches regular_expression

Motivation: When you only want to obtain a list of files that contain the matching pattern, this command is useful. It allows you to extract a list of file names that can be further used by other commands or scripts.

Explanation:

• --files-with-matches causes rg to only display the file names that contain at least one match.
• regular_expression is the pattern or string you want to search for.

Example output:

file1.txt
file2.txt

Use case 7: Show lines that do not match the given regular expression

Code:

rg --invert-match regular_expression

Motivation: There may be instances when you want to find lines that do not match a particular pattern or string. This command allows you to identify lines that don’t match the given regular expression.

Explanation:

• --invert-match causes rg to only display lines that do not match the given regular expression.
• regular_expression is the pattern or string you want to search for.

Example output:

This is a line without the regular_expression.

Use case 8: Search a literal string pattern

Code:

rg --fixed-strings -- string

Motivation: When searching for a literal string pattern, it is sometimes necessary to treat your search query as a fixed string rather than a regular expression. This command allows you to search for literal string patterns.

Explanation:

• --fixed-strings treats the search pattern as a literal string.
• -- separates the options from the search pattern.
• string is the literal string you want to search for.

Example output:

This is the line with the string.

Conclusion:

The rg command provides powerful search capabilities within files and directories. By using the various options and arguments, you can search for regular expressions, filter files, and even search for literal string patterns. This makes rg a versatile command-line tool for any developer or user who needs to find specific patterns in their files.