Overview
The `logname` command displays the name used by a user to start a login session on the system to standard output. This has a subtle but important difference from `whoami`. While `whoami` outputs the 'effective user' name currently executing the command, `logname` outputs the 'real login user' name of the session. Therefore, even after obtaining another user's privileges with `sudo` or `su` commands, `logname` will still show the name of the originally logged-in user.
Key Features
The main features of the logname command are as follows:
- Prints the user name that initiated the login session.
- Operates based on the value of the
$LOGNAMEenvironment variable. - Used to verify the actual logged-in user.
- A simple command with very few options.
Difference between logname and whoami
Both commands output user names, but show different results in privilege change scenarios.
- logname: Outputs the real logged-in user name. It does not change after using
suorsudo. - whoami: Outputs the effective user name currently executing the command. After using
suorsudo, it outputs the changed user name, such asroot.
Main Options
The `logname` command is very simple, primarily using basic help options like `--help` or `--version`.
1) Help
Generated command:
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Description:
`logname` Executes the command.
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Usage Examples
Explore various usage examples of the `logname` command to understand its functionality.
Check Current User Name
lognamePrints the name of the currently logged-in user.
Compare User Names After su Command
logname
su
whoami
lognameAfter switching to the `root` user with the `su` command, compare the output of `whoami` and `logname`. `whoami` outputs `root`, but `logname` outputs the original logged-in user name.
Installation
`logname` is part of the `coreutils` package and is included by default in most Linux distributions. No separate installation is required.
Tips & Considerations
Here are some points to consider when using the `logname` command.
Tips
- In scripts, it is recommended to use
whoamito check the privileges of the user currently executing the command, andlognameto record the actual user who logged into the system. lognamecan be used to track the real logged-in user, similar to the output of thewcommand.