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

The locate command is a powerful utility available on Unix-like operating systems that allows users to quickly search for files in their system by querying a pre-built database of filenames. This can save significant time compared to traditional methods, such as find, which search the filesystem directly. The database is typically updated periodically and contains pathnames, making locate a fast option for finding files by name.

Use case 1: Look for a pattern in the database

Code:

locate "pattern"

Motivation:

When you need to quickly find a file or files that contain a particular pattern in their filenames, the locate command becomes extremely useful. Unlike recursive search commands that traverse the directory hierarchy and can be slow, locate operates by querying an existing database of filenames, resulting in rapid search performance. This can be considerably advantageous when you need to search large filesystems or when working with constraints like limited time or system resources.

Explanation:

• locate: This is the command used to search for files in the stored database.
• "pattern": This is the specific pattern or string you are looking for in filenames. It can be part of a filename or an entire filename. When you do not include wildcard characters, locate interprets the pattern as if it were *pattern*, meaning it will search for any filenames that contain this string anywhere within them.

Example output:

/usr/local/share/doc/pattern-file.txt
/home/user/Documents/pattern-report.pdf
/var/log/pattern.log

In this output, locate has searched through the database for any filenames containing the string “pattern” and returned a series of paths where these files are located.

Use case 2: Look for a file by its exact filename

Code:

locate */filename

Motivation:

Sometimes, you know the exact filename you’re looking for, but its location within the file system is unknown or forgotten. This command allows you to find exact matches for a filename while leveraging the speed of the locate database search. In this way, it can help you efficiently gain access to the file without manually searching through directories.

Explanation:

• locate: As before, this is the command used to access the stored database of filenames.
• */filename: This pattern includes the exact filename you’re interested in. The asterisk (*) before the /filename acts as a wildcard character and denotes any preceding path. Since locate interprets it as *filename*, it will look for matches throughout any directories in your filesystem.

Example output:

/home/user/Documents/filename
/usr/local/bin/filename

Here, locate has provided the exact paths of files named “filename”, which can be found across the system in various locations.

Use case 3: Recompute the database

Code:

sudo /usr/libexec/locate.updatedb

Motivation:

The locate database contains cached information about filenames and their locations; however, it is not updated in real-time. If you have recently added files to your system and need to search for them using locate, the database needs to be refreshed to include these recent additions. This command allows users to manually update the database, ensuring that the locate command provides the most accurate and up-to-date search results.

Explanation:

• sudo: This is a command that allows a permitted user to run a command as the superuser (or another user), as specified by the security policy. Updating the locate database often requires root privileges, which is why sudo is used here.
• /usr/libexec/locate.updatedb: This executable script is responsible for updating the locate database. It must be executed with administrative rights, as it needs to access secure areas of the filesystem to index them properly.

Example output:

Rebuilding locate database... Done.

Upon execution, this command recompiles the database and includes any new files in the system, ensuring that future locate queries can return comprehensive and accurate results.

Conclusion:

The locate command offers a swift and efficient means for searching through filesystems to find files by filename. By understanding and using the various available options, users can rapidly find files based on patterns or exact filenames and ensure that their searches are current by updating the database. This makes locate a valuable tool in a user’s command-line arsenal, particularly when managing large systems or when time is crucial.