oh, and here is the sample program:
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <utmp.h>
#include <fcntl.h>
#include <pwd.h>
int massivehello(char* message)
{
int uid; //current user's id number
static int fd; //file descriptor id
FILE* fp;
char *ttydata, *user; //buffers for terminal info, and username
struct passwd *pwd; //password data structure
struct utmp *utmp; //process information structure
uid = getuid();
pwd = getpwuid(uid);
setutent(); //go to the beginning of the process list
user = pwd ? pwd->pw_name : "root"; //figure out who is running this
// go through the process list and for each entry our 'user' owns, output
// our message
while ((utmp = getutent()) != NULL)
{
if (utmp->ut_type != USER_PROCESS || //make sure it's a user process
utmp->ut_user[0] == 0 || // and there is a valid user
(strcmp(utmp->ut_user, user))) // and that user is our 'user'
{
continue; // skip this entry if any of that stuff failed
}
sprintf(ttydata, "/dev/%s", utmp->ut_line);
//ttydata is the name of the terminal to write to
fd = open(ttydata, O_WRONLY | O_NDELAY);
if ((fp = fdopen(fd,"w")) != NULL)
{
fputs(message, fp);
fclose(fp);
}
else
{
close(fd);
}
}
endutent(); //close the utmp file
return 0;
}
int main()
{
int retval = 0;
retval = massivehello("Hello World!\n");
return(retval);
}
a question about gdb
