ac

Print how long the current user has been connected in hours

$ ac

$ ac -p

$ ac -p [username]

$ ac -d -p [username]

$ ac --compatibility

ac [-d] [-p] [-y] [-f filename] [-a] [--compatibility] [people]

ac generates a report of connect time in hours based on the logins and logouts recorded in the system's wtmp file. It calculates the difference between login and logout timestamps to determine how long each user has been connected. Output can be broken down by individual user, by day, or presented as an aggregate total. The wtmp file is maintained automatically by login-related system utilities such as login, sshd, and init.

-d, --daily-totals

Display totals for each calendar day instead of a single aggregate total

Show connection time for each user separately plus overall total

Calculate combined connect time for specified usernames (space-separated list)

Read accounting data from specified file instead of system wtmp

Include daily records even when no login activity occurred

Display year alongside date information

Print category totals that equal zero

Display errors when wtmp file contains anomalies

Include time accrued between user login and system reboot events

Count time from login to next login when logout records are missing

Include time when chronological inconsistencies occur in wtmp

Enable all three compatibility flags (reboots, supplants, timewarps)

Connect time calculations depend on accurate wtmp records. System crashes or improper shutdowns may result in incomplete or inaccurate data.

Part of GNU Accounting Utilities, based on traditional UNIX accounting tools. The GNU version offers enhanced functionality compared to traditional implementations.

last(1), lastlog(8), login(1), sa(8), wtmp(5)