CONTENTS

SYNOPSIS

struct utmp *getutent(void);
"struct utmp *getutid(struct utmp *"ut);
"struct utmp *getutline(struct utmp *"ut);

"struct utmp *pututline(struct utmp *"ut);

void setutent(void);
void endutent(void);

setutent() rewinds the file pointer to the beginning of the utmp file. It is generally a Good Idea to call it before any of the other functions.

endutent() closes the utmp file. It should be called when the user code is done accessing the file with the other functions.

getutent() reads a line from the current file position in the utmp file. It returns a pointer to a structure containing the fields of the line.

getutid() searches forward from the current file position in the utmp file based upon ut. If ut->ut_type is RUN_LVL, BOOT_TIME, NEW_TIME, or OLD_TIME, getutid() will find the first entry whose ut_type field matches ut->ut_type. If ut->ut_type is one of INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS, getutid() will find the first entry whose ut_id field matches ut->ut_id.

getutline() searches forward from the current file position in the utmp file. It scans entries whose ut_type is USER_PROCESS or LOGIN_PROCESS and returns the first one whose ut_line field matches ut->ut_line.

EXAMPLE

#include <string.h>
#include <stdlib.h>
#include <pwd.h>
#include <unistd.h>
#include <utmp.h>

int main(int argc, char *argv[])
{
struct utmp entry;

system("echo before adding entry:;who");

entry.ut_type=USER_PROCESS;
entry.ut_pid=getpid();
strcpy(entry.ut_line,ttyname(0)+strlen("/dev/"));
/* only correct for ptys named /dev/tty[pqr][0-9a-z] */
strcpy(entry.ut_id,ttyname(0)+strlen("/dev/tty"));
time(&entry.ut_time);
strcpy(entry.ut_user,getpwuid(getuid())->pw_name);
memset(entry.ut_host,0,UT_HOSTSIZE);
entry.ut_addr=0;
setutent();
pututline(&entry);

system("echo after adding entry:;who");

entry.ut_type=DEAD_PROCESS;
memset(entry.ut_line,0,UT_LINESIZE);
entry.ut_time=0;
memset(entry.ut_user,0,UT_NAMESIZE);
setutent();
pututline(&entry);

system("echo after removing entry:;who");

"CONFORMING TO"

In XPG2 and SVID2 the function pututline() is documented to return void, and that is what it does on many systems (AIX, HPUX, Linux libc5). HPUX introduces a new function _pututline() with the prototype given above for pututline() (also found in Linux libc5).

All these functions are obsolete now on non-Linux systems. POSIX 1003.1-2001, following XPG4.2, does not have any of these functions, but instead uses

#include <utmpx.h>

struct utmpx *getutxent(void);
struct utmpx *getutxid(const struct utmpx *);
struct utmpx *getutxline(const struct utmpx *);
struct utmpx *pututxline(const struct utmpx *);
void setutxent(void);
void endutxent(void);

The utmpx structure is a superset of the utmp structure, with additional fields, and larger versions of the existing fields. The corresponding files are often /var/*/utmpx and /var/*/wtmpx.