cis-lclient06:~/class/nov22>more exec8.c
#include <syscall.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define SIZE 40
int main(void) {
    char buf[SIZE+1], argv0[SIZE], argv1[SIZE], argv2[SIZE]; 
    int argc;
    printf("\n->");
    if (gets(buf) == (char *) NULL) exit(1); /* GETS IS UNSAFE */
    argv0[0] = '\0';
    argc = sscanf(buf, "%s %s %s", argv0, argv1, argv2);
    printf("argc = %d, strlen(argv0) = %d\n", argc, strlen(argv0));
    switch (argc) {
       case 1:
          execlp(argv0, argv0, (char *) NULL); 
          printf("argc = %d, strlen(argv0) = %d\n", argc, strlen(argv0));
          break;
       case 2:
          execlp(argv0, argv0, argv1, (char *) NULL); 
          break;
       case 3:
          execlp(argv0, argv0, argv1, argv2, (char *) NULL); 
          break;
   }
   printf("%s: command not found\n", argv0);
}

cis-lclient06:~/class/nov22>gcc exec8.c
/tmp/ccUJ4lr5.o: In function `main':
exec8.c:(.text+0x24): warning: the `gets' function is dangerous and should not be used.
cis-lclient06:~/class/nov22>./a.out
->ps
argc = 1, strlen(argv0) = 2
  PID TTY          TIME CMD
14862 pts/1    00:00:00 tcsh
16404 pts/1    00:00:00 ps
cis-lclient06:~/class/nov22>./a.out
->ps -lax
argc = 2, strlen(argv0) = 2
Warning: bad syntax, perhaps a bogus '-'? See /usr/share/doc/procps-3.2.8/FAQ
F   UID   PID  PPID PRI  NI    VSZ   RSS WCHAN  STAT TTY        TIME COMMAND
4     0     1     0  20   0   2924  1260 poll_s Ss   ?          0:02 /sbin/init
1     0     2     0  20   0      0     0 kthrea S    ?          0:00 [kthreadd]
1     0     3     2 -100  -      0     0 migrat S    ?          0:00 [migration/0]
1     0     4     2  20   0      0     0 run_ks S    ?          0:53 [ksoftirqd/0]
...
cis-lclient06:~/class/nov22>