Standard Input/Output (I/O)

An extended actor may take advantage of the entire C library for dealing with I/O. In addition to the I/O interface provided by the C library, an extended actor may also use POSIX I/O services such as open, read, or write, as well as POSIX socket services such as socket, bind, and connect.

The following program may be run as an actor, and illustrates the way in which the C library might be used from an actor.

Example 5-2 Using the C Library from an Actor

#include <stdio.h
#include <stdlib.h>
#include <chorus/stat.h>

#define  BUF_SIZE 80

struct stat st;

int main(int argc, char** argv, char** envp)
{
   FILE* file;
   FILE* filew;
   char* buf;
   int res;

   if (argc != 2 && argc != 3) {
      fprintf(stderr, "Usage: %s filename\n", argv[0]);
      exit(1);
   }

   file = fopen(argv[1], "r");

   if (file == NULL) {
      fprintf(stderr, "Cannot open file %s\n", argv[1]);
      exit(1);
   }

   res = stat(argv[1], &st);
   if (res < 0) {
      fprintf(stderr, "Cannot stat file\n");
      exit(1);
   }

   printf("File size is %d mode 0x%x\n", st.st_size, st.st_mode);

   buf = (char*) malloc(BUF_SIZE);
   if (buf == NULL) {
      fprintf(stderr, "Cannot allocate buffer\n");
      exit(1);
   }

   bzero(buf, BUF_SIZE);
   res = read(fileno(file), buf, 80);
   if (res == -1) {
      fprintf(stderr, "Cannot read file\n");
      exit(1);
   }

   printf("%s\n", buf);

   if (argv[2] != NULL) {
      filew = fopen(argv[2], "w");

      if (filew == NULL) {
         fprintf(stderr, "Cannot open file %s\n", argv[2]);
         exit(1);
      }

      printf("Type any input you like: \n");

      do {
         scanf("%80s", buf);
         printf("buf=%s\n", buf);
         fprintf(filew, "%s", buf);
         printf("buf=%s\n", buf);
      } while (buf[0] != 'Q');
   }
   exit(0);
}

This example assumes that argv[0] is valid, and the actor is linked with the ~lib/classix/libcx.a library, since the library is common to both user and supervisor actors. Referencing argv[0] without checking if argc is greater than zero can cause the actor to make an exception and be deleted.