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GETUTENT (3)

access utmp file entries

SYNOPSIS

#include <utmp.h>

struct utmp *getutent(void);

struct utmp *getutid(struct utmp * ut );

struct utmp *getutline(struct utmp * ut );

void pututline(struct utmp * ut );

void setutent(void);

void endutent(void);

void utmpname(const char * file );

DESCRIPTION

utmpname

_PATH_UTMP

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.

pututline() writes the utmp structure ut into the utmp file. It uses getutid() to search for the proper place in the file to insert the new entry. If it cannot find an appropriate slot for ut, pututline() will append the new entry to the end of the file.

RETURN VALUE

getutent

getutid

getutline

static struct utmp

ERRORS

(struct utmp*)0

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");

  endutent();
  return 0;
}

FILES

CONFORMING TO

XPG 2, SVID 2, Linux FSSTND 1.2