How to Use the Command 'ac' (with Examples)

The ac command is a versatile utility in Unix-like operating systems that allows users to track how long they or others have been connected to the system. It’s particularly useful for system administrators who need to monitor user activity for resource management, auditing, or billing purposes. By leveraging various options, users can generate detailed reports on connectivity duration, down to specific users and time frames. Let’s delve into specific use cases for the ac command and explore how they can be utilized effectively.

Use Case 1: Print How Long the Current User Has Been Connected in Hours

Code:

ac

Motivation: Executing the ac command without any options provides a quick way for users to check how many hours they have been connected to the system. This is especially useful if a user wants to manage their work sessions effectively by monitoring their connection duration over time.

Explanation:

• Running ac without options gives an aggregate of all logged-in time for the current user. This command relies on the /var/log/wtmp file, which logs login and logout events.

Example Output:

     16.45

The output indicates that the current user has been logged in for 16.45 hours in total.

Use Case 2: Print How Long Users Have Been Connected in Hours

Code:

ac -p

Motivation: System administrators or managers might want to oversee the logged-in times of all users to identify usage patterns, charge for compute hours, or ensure fair usage of system resources. Using ac -p provides a comprehensive view of all users’ connectivity times.

Explanation:

• The -p option lists the total logged-in hours for each user instead of just the current user. This usage aggregates the connection times for all users recorded in the system’s logs.

Example Output:

user1   45.34
user2   30.12
user3    5.67

This output shows that user1 has been connected for 45.34 hours, user2 for 30.12 hours, and user3 for 5.67 hours.

Use Case 3: Print How Long a Particular User Has Been Connected in Hours

Code:

ac -p username

Motivation: When monitoring or troubleshooting specific accounts, administrators may need to focus on individual users’ connection times. By specifying a username, they can retrieve usage statistics that are pertinent only to the user of interest.

Explanation:

• The -p option here, followed by a username, isolates the connection report to the specified user. This feature is crucial for scenarios where pinpointing the usage of a particular account is necessary.

Example Output:

username   12.89

This output indicates that the user username has been logged in for 12.89 hours.

Use Case 4: Print How Long a Particular User Has Been Connected in Hours per Day (With Total)

Code:

ac -dp username 

Motivation: Monitoring user activity on a day-to-day basis can provide insights into daily usage patterns, helping in optimizing resource allocation and enhancing security measures. This option can be especially valuable for businesses that need detailed records for auditing purposes.

Explanation:

• The -d option breaks down the connectivity time on a per-day basis. Combined with -p and a username, it delivers detailed daily statistics as well as the total logged-in time for a specific account.

Example Output:

Aug 15, 2023  3.45
Aug 16, 2023  4.23
...
total  23.67

This output showcases the daily logged-in hours for username on specified dates, summing up to a total of 23.67 hours.

Conclusion:

The ac command is a powerful tool for monitoring user activity and managing system resources effectively. With its ability to report usage statistics specific to users and timeframes, it serves as an invaluable utility for system administrators and users alike. Whether for personal time management or detailed resource auditing, the ac command can be customized to meet a wide array of needs by simply leveraging its options.