books/apue/fd-flags.c

   1 /*
   2  * Print flags for specified file-descriptor
   3  */
   4 #include <stdio.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7 #include <stdlib.h>
   8 #include <fcntl.h>
   9 #include <errno.h>
  10 #include <sys/types.h>
  11
  12 int main(int argc, char *argv[])
  13 {
  14         int accmode, val;
  15
  16         if (argc != 2) {
  17                 fprintf(stderr, "usage: a.out <descriptor#>\n");
  18                 exit(1);
  19         }
  20
  21         if ((val = fcntl(atoi(argv[1]), F_GETFL, 0)) < 0) {
  22                 fprintf(stderr, "fcntl error for fd %d: %s\n", atoi(argv[1]),
  23                         strerror(errno));
  24                 exit(1);
  25         }
  26
  27         accmode = val & O_ACCMODE;
  28         if (accmode == O_RDONLY)
  29                 printf("read only");
  30         else if (accmode == O_WRONLY)
  31                 printf("write only");
  32         else if (accmode == O_RDWR)
  33                 printf("read write");
  34         else
  35                 printf("unknow access mode");
  36
  37         if (val & O_APPEND)
  38                 printf(", append");
  39
  40         if (val & O_NONBLOCK)
  41                 printf(", nonblocking");
  42
  43         if (val & O_SYNC)
  44                 printf(", synchornous writes");
  45
  46         putchar('\n');
  47         return 0;
  48 }