One Linux command per day (+): Whereis

1. Introduction to Commands

Whereis (whereis) command is used to locate instructions for the path of the binaries, source code files, and the Man manual page and other related files.

The Whereis command can only be used for program name searches, and only binary files (parameter-B), man description file (parameter-m), and source code file (parameter-s) are searched. If the argument is omitted, all information is returned.

Whereis looks very fast when compared to find, because the Linux system records all the files in the system in a single database file, and when you use Whereis and the locate described below, the data is looked up from the database, not like the Find command. By traversing the hard drive to find, the efficiency will naturally be very high. However, the database file is not updated in real time and is updated once a week by default, so when we use Whereis and locate to find files, we sometimes find data that has been deleted, or just created the file, but cannot find it because the database file is not updated.

2. Usage

Whereis dir ...-f] name ...

3. Options

-B< catalogue >

-M< catalogue >

-S< catalogue >

-U: Finds files that do not contain the specified type.

4. Example 1: View the default JDK

Whereis/usr/local/tomcat

Example 2: Only binary files are found

Whereis -b  /usr/local/tomcat

One Linux command per day (+): Whereis