---
name: "utmp"
section: "5"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "openbsd", "macos"]
url: "https://new.carta.tech/utmp"
---

# utmp(5)

login records (DEPRECATED)

## NAME

**utmp**, **wtmp**, **lastlog** – login records (DEPRECATED)

## SYNOPSIS

**#include \<utmp.h\>**

## DESCRIPTION

The interfaces in file ⟨*utmp.h*⟩ are all **DEPRECATED** and are only provided for compatibility with previous releases of Mac OS X. See [pututxline(3)](/pututxline/3.md) and [utmpx(5)](/utmpx/5.md) for the supported interfaces.

⟨*utmp.h*⟩ declares the structures used to record information about current users in the file **utmp**, logins and logouts in the file **wtmp**, and last logins in the file **lastlog**. The time stamps of date changes, shutdowns and reboots are also logged in the **wtmp** file.

These files can grow rapidly on busy systems, daily or weekly rotation is recommended.  If any of these files do not exist, it is not created. These files must be created manually and are normally maintained in either the script */etc/daily* or the script */etc/weekly*. (See [cron(8)](/cron/8.md).)

```
#define _PATH_UTMP      "/var/run/utmp"
#define _PATH_WTMP      "/var/log/wtmp"
#define _PATH_LASTLOG   "/var/log/lastlog"
#define UT_NAMESIZE     8
#define UT_LINESIZE     8
#define UT_HOSTSIZE     16
struct lastlog {
        time_t  ll_time;
        char    ll_line[UT_LINESIZE];
        char    ll_host[UT_HOSTSIZE];
};
struct utmp {
        char    ut_line[UT_LINESIZE];
        char    ut_name[UT_NAMESIZE];
        char    ut_host[UT_HOSTSIZE];
        time_t	ut_time;
};
```

Each time a user logs in, the login program looks up the user's UID in the file **lastlog.** If it is found, the timestamp of the last time the user logged in, the terminal line and the hostname are written to the standard output. (Providing the login is not *quiet*, see [login(1)](/login/1.md).) The login program then records the new login time in the file **lastlog**.

After the new *lastlog* record is written , the file **utmp** is opened and the *utmp* record for the user inserted. This record remains there until the user logs out at which time it is deleted. The **utmp** file is used by the programs [rwho(1)](/rwho/1.md), [users(1)](/users/1.md), [w(1)](/w/1.md), and [who(1)](/who/1.md).

Next, the login program opens the file **wtmp**, and appends the user's *utmp* record. The same *utmp* record, with an updated time stamp is later appended to the file when the user logs out. (See launchd(8).) The **wtmp** file is used by the programs [last(1)](/last/1.md) and [ac(8)](/ac/8.md).

In the event of a date change, a shutdown or reboot, the following items are logged in the **wtmp** file.

- reboot

  - shutdown

  A system reboot or shutdown has been initiated. The character ‘~’ is placed in the field *ut\_line*, and reboot or shutdown in the field *ut\_name*. (See [shutdown(8)](/shutdown/8.md) and [reboot(8)](/reboot/8.md).)

- date

  The system time has been manually or automatically updated. (See [date(1)](/date/1.md).) The command name date is recorded in the field *ut\_name*. In the field *ut\_line*, the character ‘\\\*(Ba’ indicates the time prior to the change, and the character ‘{’ indicates the new time.

## FILES

(These files no longer exist in 10.5 or later.)

- */var/run/utmp*

  The **utmp** **file.**

- */var/log/wtmp*

  The **wtmp** **file.**

- */var/log/lastlog*

  The **lastlog** **file.**

## SEE ALSO

[last(1)](/last/1.md), [login(1)](/login/1.md), [who(1)](/who/1.md), [ac(8)](/ac/8.md), launchd(8)

## HISTORY

A **utmp** and **wtmp** file format appeared in Version 6 AT&T UNIX. The **lastlog** file format appeared in 3.0BSD.