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updwtmp(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|FILES \|ATTRIBUTES \|VERSIONS \|STANDARDS \|HISTORY \|SEE ALSO \|COLOPHON

updwtmp(3)               Library Functions Manualupdwtmp(3)

NAME top

       updwtmp, logwtmp - append an entry to the wtmp file

LIBRARY top

       System utilities library (libutil,-lutil)

SYNOPSIS top

#include <utmp.h>void updwtmp(const char *wtmp_path, const struct utmp *ut);void logwtmp(const char *line, const char *name, const char *host);

DESCRIPTION top

updwtmp() appends the utmp structureut to the wtmp file.logwtmp() constructs a utmp structure usingline,name,host,       current time, and current process ID.  Then it callsupdwtmp() to       append the structure to the wtmp file.

FILES top

/var/log/wtmp              database of past user logins

ATTRIBUTES top

       For an explanation of the terms used in this section, seeattributes(7).       ┌─────────────────────┬───────────────┬──────────────────────────┐       │Interface│Attribute│Value│       ├─────────────────────┼───────────────┼──────────────────────────┤       │updwtmp(),          │ Thread safety │ MT-Unsafe sig:ALRM timer │       │logwtmp()           │               │                          │       └─────────────────────┴───────────────┴──────────────────────────┘

VERSIONS top

       For consistency with the other "utmpx" functions (seegetutxent(3)), glibc provides (since glibc 2.1):#define _GNU_SOURCE/* See feature_test_macros(7) */#include <utmpx.h>void updwtmpx (const char *wtmpx_path, const struct utmpx *utx);       This function performs the same task asupdwtmp(), but differs in       that it takes autmpx structure as its last argument.

STANDARDS top

       None.

HISTORY top

       Solaris, NetBSD.

COLOPHON top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17updwtmp(3)

Pages that refer to this page:utmp(5)

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