updwtmp(3) Library Functions Manual updwtmp(3)
NAME
updwtmp, logwtmp - append an entry to the wtmp file
LIBRARY
System utilities library (libutil, -lutil)
SYNOPSIS
#include <utmp.h>
void updwtmp(const char *wtmp_file, const struct utmp *ut);
void logwtmp(const char *line, const char *name, const char *host);
DESCRIPTION
updwtmp() appends the utmp structure ut to the wtmp file.
logwtmp() constructs a utmp structure using line, name, host, current
time, and current process ID. Then it calls updwtmp() to append the
structure to the wtmp file.
FILES
/var/log/wtmp
database of past user logins
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌───────────────────────────┬───────────────┬──────────────────────────┐
│ Interface │ Attribute │ Value │
├───────────────────────────┼───────────────┼──────────────────────────┤
│ updwtmp(), logwtmp() │ Thread safety │ MT-Unsafe sig:ALRM timer │
└───────────────────────────┴───────────────┴──────────────────────────┘
VERSIONS
For consistency with the other "utmpx" functions (see getutxent(3)),
glibc provides (since glibc 2.1):
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <utmpx.h>
void updwtmpx (const char *wtmpx_file, const struct utmpx *utx);
This function performs the same task as updwtmp(), but differs in that
it takes a utmpx structure as its last argument.
STANDARDS
None.
HISTORY
Solaris, NetBSD.
SEE ALSO
getutxent(3), wtmp(5)
Linux man-pages 6.9.1 2024-05-02 updwtmp(3)
Generated by dwww version 1.16 on Tue Dec 16 04:18:59 CET 2025.