% cat  system.c

/* A program to demonstrate some of the nifty UNIX capabilities in C */

#include <stdio.h>

main()

{
  char tmp[100];

  printf("About to call the system command, press enter");
  gets(tmp);

  system("ls -l");

  printf("Just came back from the system command\n");
  
}

% cc  system.c
% a.out 
About to call the system command, press enter
-rwx------   1 crs      cl          4669 Aug 16 11:11 a.out
-rw-------   1 crs      cl           682 Aug 16 09:13 fun3.c
-rw-------   1 crs      cl          1652 Dec  7 1993  gradepretty.c
-rw-------   1 crs      cl           110 Dec  7 1993  gradepretty.dat
-rw-------   1 crs      cl           985 Dec  8 1993  grades.c
-rw-------   1 crs      cl           402 Aug 16 11:10 popen.c
-rw-------   1 crs      cl           442 Dec  7 1993  quad.c
-rw-------   1 crs      cl           810 Aug 16 10:43 quadfun.c
-rw-------   1 crs      cl          1009 Dec  7 1993  quadsub.C
-rw-------   1 crs      cl           578 Dec  7 1993  tempconv.c
Just came back from the system command
%