How to Use the Command 'w' (with examples)

The w command is a powerful tool used in Unix-like operating systems to display information about current users logged into the system. It provides insights into user activities, including who is logged on and what they are doing, making it a helpful tool for system administrators and users to monitor system usage. The command outputs data such as the username, terminal line (TTY), remote host, login time, idle time, and current process. Its ability to present this data is crucial for security monitoring, resource management, and system auditing purposes.

Use case 1: Show logged-in users information

Code:

w

Motivation:

The primary motivation for using the w command in its simplest form is to gain an overview of current users logged into the system and their activities. This is crucial for system administrators who need to keep track of system usage and ensure it is being used appropriately. Knowing which users are active can help in deciding when to perform system maintenance and can serve as a first step for diagnosing system performance issues.

Explanation:

• w: The command itself, without any additional arguments, provides a straightforward snapshot of the system’s active users and their activities. It includes a header that shows the current time, system uptime, the number of users logged in, and average system loads. Below the header, each logged-in user’s details are listed, which include:
  • User name
  • TTY: Terminal line
  • Remote host: The originating host from where the user connected
  • Login time: The time at which the user logged in
  • Idle time: The duration for which the user has been idle
  • JCPU/PCPU: Time spent in terminal/command process
  • Current process: The command currently being executed by the user

Example output:

 15:20:07 up 10 days, 23:08,  3 users,  load average: 0.27, 0.20, 0.16
USER    TTY      FROM      LOGIN@   IDLE   JCPU   PCPU WHAT
john    pts/0    :0.0      10:30    0.00s  0.08s  0.01s bash
jane    tty2     -         09:15    1:44m  0.05s  0.04s -bash
admin   pts/1    192.168.1.5 13:50   0.01s  0.02s  0.01s w

Use case 2: Show logged-in users information without a header

Code:

w -h

Motivation:

In certain scenarios, users may want a cleaner output without the summary header that is usually at the top of the w command’s output. This is especially useful when piping the output to another command or file for processing or when the primary interest lies in the user details themselves, without the overall system statistics. The absence of the header can also reduce clutter in scripts or logs that are being monitored.

Explanation:

• -h: The -h flag tells the w command to omit the header from its output. By using this option, all that is displayed is the list of logged-in users and their activity, sans any system load or uptime information.

Example output:

USER    TTY      FROM      LOGIN@   IDLE   JCPU   PCPU WHAT
john    pts/0    :0.0      10:30    0.00s  0.08s  0.01s bash
jane    tty2     -         09:15    1:44m  0.05s  0.04s -bash
admin   pts/1    192.168.1.5 13:50   0.01s  0.02s  0.01s w

Use case 3: Show information about logged-in users, sorted by their idle time

Code:

w -i

Motivation:

Sorting users by their idle time can be particularly useful in identifying which users have been inactive for the longest periods. This information can be crucial for system administrators in deciding whether to end certain user sessions to free up system resources. It also helps in potentially identifying abandoned sessions that could pose a security risk if unattended.

Explanation:

• -i: The -i option sorts the users by their idle time. This ordering prioritizes the display based on how long users have been inactive, placing the users with the longest idle time at the bottom of the list. This perspective allows administrators to quickly recognize and address any sessions that have remained unattended for an extended period.

Example output:

USER    TTY      FROM      LOGIN@   IDLE   JCPU   PCPU WHAT
john    pts/0    :0.0      10:30    0.00s  0.08s  0.01s bash
admin   pts/1    192.168.1.5 13:50   0.01s  0.02s  0.01s w
jane    tty2     -         09:15    1:44m  0.05s  0.04s -bash

Conclusion:

The w command is a versatile and essential tool for managing user activities on Unix-like systems. Its various options allow users and administrators to customize the command’s output to suit particular needs, whether it’s a simple overview, a header-free output, or sorting by idle time. By understanding these use cases, command users can enhance their ability to monitor and manage system usage effectively.