logname

file managementLinux/Unix

The logname command is one of the most frequently used commands in Linux/Unix-like operating systems. logname Print the name of the current user

See Examples View Syntax

Quick Reference

Command Name:

logname

Category:

file management

Platform:

Linux/Unix

Basic Usage:

logname [options] [arguments]

Common Use Cases

Syntax

logname [options]

Options

Option	Description
`--help`	Display help information and exit
`--version`	Display version information and exit

Examples

How to Use These Examples

The examples below show common ways to use the logname command. Try them in your terminal to see the results. You can copy any example by clicking on the code block.

# Basic Examples Basic

logname

Display the current login name.

# Advanced Examples Advanced

if [ "$(logname)" = "admin" ]; then echo "Administrative user"; fi

Use logname in a script to check the login name.

logname > current_user.txt Save the login name to a file. echo "Current login name: $(logname)" Include the login name in a message. sudo logname Display the original login name, even when running with sudo.

Try It Yourself

Practice makes perfect! The best way to learn is by trying these examples on your own system with real files.

Understanding Syntax

Pay attention to the syntax coloring: commands, options, and file paths are highlighted differently.

Notes

The 'logname' command is a simple utility that prints the name of the current user, specifically the login name rather than the effective username. This distinction is important in environments where users might switch identities using commands like 'su' or 'sudo'. Key features of the logname command: 1. Login Name Identification: logname reports the original login name of the user who started the current session, not the current effective user ID which might be different due to privilege escalation or user switching. 2. Consistency: Unlike 'whoami', which shows the current effective user, logname always shows the original login user regardless of subsequent user identity changes within the session. 3. Simple Interface: With no arguments needed for basic operation and minimal options, logname is designed for simplicity and reliability. 4. Security Information: The command provides a reliable way to determine who initially authenticated to the system, which can be valuable for security auditing and access control. 5. Integration with Scripts: logname is particularly useful in shell scripts that need to know the original user identity, regardless of privilege escalation. 6. Standard Compliance: The command follows the POSIX standard, ensuring consistent behavior across different Unix-like operating systems. 7. Error Handling: If the login name cannot be determined (for example, if the process wasn't started from a login session), logname will exit with an error status. Common use cases for the logname command include: - Identifying the original user in scripts that may be run with elevated privileges - Recording the initiating user in log files or audit trails - Determining ownership for files created by processes with changed user IDs - Access control decisions based on the original authenticated user - User-specific customization in system-wide scripts - Troubleshooting user identity issues in multi-user environments The logname command gets its information from the system's utmp file, which records login sessions. It's a reliable way to determine who initially logged in, even after multiple user identity changes within a session. For security-conscious administrators and developers, understanding the difference between logname (original login user) and whoami (current effective user) is crucial for implementing proper access controls and audit trails in systems where users may operate with different identities.

Related Commands

These commands are frequently used alongside logname or serve similar purposes:

Use Cases

Learn By Doing

The best way to learn Linux commands is by practicing. Try out these examples in your terminal to build muscle memory and understand how the logname command works in different scenarios.

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$ logname

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