ipc/popen_ls.c

   1 #include <err.h>         /* for errx() */
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include <sys/wait.h>    /* for waitpid() macros */
   5
   6 #define MAX_STR 100
   7
   8 int main(void)
   9 {
  10     char str[MAX_STR];
  11     int ret;
  12     FILE *fp;
  13
  14     /* Initiate pipe stream to ``ls'' */
  15     fp = popen("ls", "r");
  16     if (fp == NULL)
  17         errx(EXIT_FAILURE, "popen()");
  18
  19     /* Read from stream */
  20     while (fgets(str, MAX_STR, fp) != NULL) {
  21         printf("%s", str);
  22     }
  23
  24     /* Close pipe stream */
  25     ret = pclose(fp);
  26     if  (ret == -1) {
  27         errx(EXIT_FAILURE, "pclose()");
  28     }
  29     else {
  30         /*
  31          * Use macros described under wait() to inspect the return value
  32          * of pclose() in order to determine success/failure of command
  33          * executed by popen().
  34          */
  35
  36         if (WIFEXITED(ret)) {
  37             printf("Child exited, ret = %d\n", WEXITSTATUS(ret));
  38         } else if (WIFSIGNALED(ret)) {
  39             printf("Child killed, signal %d\n", WTERMSIG(ret));
  40         } else if (WIFSTOPPED(ret)) {
  41             printf("Child stopped, signal %d\n", WSTOPSIG(ret));
  42         }
  43         /* Not all implementations support this */
  44 #ifdef WIFCONTINUED
  45         else if (WIFCONTINUED(ret)) {
  46             printf("Child continued\n");
  47         }
  48 #endif
  49         /* Non standard case -- may never happen */
  50         else {
  51             printf("Unexpected return value, ret = 0x%x\n", ret);
  52         }
  53     }
  54
  55     return EXIT_SUCCESS;
  56 }