UPDWTMP(3) Linux Programmer's Manual UPDWTMP(3)
updwtmp, logwtmp - append an entry to the wtmp file
void updwtmp(const char *wtmp_file, const struct utmp *ut);
void logwtmp(const char *line, const char *name, const char *host);
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.
database of past user logins
Not in POSIX.1-2001. Present on Solaris, NetBSD, and perhaps other systems.
Both functions are available under glibc2, but not under libc5. However, logwtmp() used
to occur in the old libbsd. These days, the logwtmp() function is included in libutil.
(Hence you'll need to add -lutil to your compiler command line to get it.)
For consistency with the other "utmpx" functions (see getutxent(3)), glibc provides (since
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.
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GNU 2008-07-02 UPDWTMP(3)