Identity crisis: The manual page in UNIX for who lists who am i as an acceptable *usage of * the command. It also lists whoami. Modify who2.c so it supports the who am i *usage. Write a C program that works like whoami.

The who2.c file is:

#include #include #include #include #include

/* #define SHOWHOST */

void showtime(long); void show_info(struct utmp *);

int main() { struct utmp utbuf; /* read info into here */ int utmpfd; /* read from this descriptor */

if ( (utmpfd = open(UTMP_FILE, O_RDONLY)) == -1 ){ perror(UTMP_FILE); exit(1); }

while( read(utmpfd, &utbuf, sizeof(utbuf)) == sizeof(utbuf) ) show_info( &utbuf ); close(utmpfd); return 0; } /* * show info() * displays the contents of the utmp struct * in human readable form * * displays nothing if record has no user name */ void show_info( struct utmp *utbufp ) { if ( utbufp->ut_type != USER_PROCESS ) return;

printf("%-8.8s", utbufp->ut_name); /* the logname */ printf(" "); /* a space */ printf("%-8.8s", utbufp->ut_line); /* the tty */ printf(" "); /* a space */ showtime( utbufp->ut_time ); /* display time */ #ifdef SHOWHOST if ( utbufp->ut_host[0] != '\0' ) printf(" (%s)", utbufp->ut_host);/* the host */ #endif printf(" "); /* newline */ }

void showtime( long timeval ) /* * displays time in a format fit for human consumption * uses ctime to build a string then picks parts out of it * Note: %12.12s prints a string 12 chars wide and LIMITS * it to 12chars. */ { char *cp; /* to hold address of time */

cp = ctime(&timeval); /* convert time to string */ /* string looks like */ /* Mon Feb 4 00:46:40 EST 1991 */ /* 0123456789012345. */ printf("%12.12s", cp+4 ); /* pick 12 chars from pos 4 */ }