logname

Additional Notes

logname prints the name of the user who initially logged into the current terminal session. Unlike whoami (which returns the effective user ID) and id -un (which also returns the effective username), logname always shows the original login name, regardless of su, sudo, or other user-switching commands.

It works by reading the /var/run/utmp or /var/log/wtmp file, or by checking the LOGNAME environment variable.

Syntax

logname [options]

Parameters

• options: Flags that change how logname behaves.
• target: Optional file, device, interface, user, service, or command target when the command supports one.

Common Options

• --help: Display help and exit.
• --version: Output version information and exit.

Examples

logname

Output: rani (the original login user).

sudo su
logname

Even after switching to root, logname still shows the original login name.

echo $(logname)

Use in a command substitution to capture the login name.

Practical Notes

• logname differs from whoami and id -un when privileges have been escalated. If you are root via sudo, whoami shows root, but logname shows the original user.
• If the login name cannot be determined, logname exits with a non-zero status and prints an error.
• The LOGNAME environment variable is set by the login process and is not always reliable if tampered with.