1 jelson 1.1 /*
 2             * nbcat: a simple program similar to 'cat', but which uses
 3             * nonblocking reads.
 4             *
 5             * This utility can be used to copy the current contents of an emlog
 6             * device without blocking to wait for more input.  For example:
 7             *
 8             *        nbcat /var/log/emlog-device-instance > /tmp/saved-log-file
 9             *
10             * ...will copy the current contents of the named emlog device to a
11             * file in /tmp.
12             *
13             * This code is freeware and may be distributed without restriction.
14             *
15             * Jeremy Elson <jelson@circlemud.org>
16             * August 11, 2001

17 jelson 1.2  *
18             * $Id$

19 jelson 1.1  */
20            
21            #include <stdio.h>
22            #include <stdlib.h>
23            #include <unistd.h>
24            #include <fcntl.h>
25            #include <errno.h>
26            
27            int main(int argc, char *argv[])
28            {
29              int fd, retval;
30              char buf[4096];
31            
32              if (argc != 2) {
33                fprintf(stderr, "usage: %s <filename>\n", argv[0]);
34                exit(1);
35              }
36            
37              if ((fd = open(argv[1], O_RDONLY | O_NONBLOCK)) < 0) {
38                perror(argv[1]);
39                exit(1);
40 jelson 1.1   }
41            
42              while ((retval = read(fd, buf, sizeof(buf))) > 0) {
43                if (write(STDOUT_FILENO, buf, retval) < 0) {
44                  perror("writing to stdout");
45                  break;
46                }
47              }
48            
49              if (retval < 0 && errno != EAGAIN) {
50                perror(argv[1]);
51                exit(1);
52              }
53            
54              return 0;
55            }