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  1. #include <errno.h>     // errno, EINTR
  2. #include <stdio.h>     // perror
  3. #include <stdlib.h>    // exit
  4. #include <unistd.h>    // _exit, close, dup2, execl, fork, pipe, STDOUT_FILENO
  5. #include <sys/wait.h>  // wait, pid_t
  6.  
  7.  
  8. void handle_child_process_output(char *buffer, ssize_t count);
  9.  
  10. int main(void)
  11. {
  12.     int filedes[2];
  13.     if (pipe(filedes) == -1)
  14.     {
  15.         perror("pipe");
  16.         exit(EXIT_FAILURE);
  17.     }
  18.     pid_t pid = fork();
  19.     if (pid == -1)
  20.     {
  21.         perror("fork");
  22.         exit(EXIT_FAILURE);
  23.     }
  24.     else if (pid == 0)
  25.     {
  26.         while ((dup2(filedes[1], STDOUT_FILENO) == -1 && (errno == EINTR)))
  27.         {
  28.             continue;
  29.         }
  30.         fprintf(stdout,"point 1\n");
  31.  
  32.         close(filedes[1]);
  33.         close(filedes[0]);
  34.         fprintf(stdout,"point 2\n");
  35.  
  36.         static char *argv[] = {"echo", "Sphinx of black quartz, judge my vow.", NULL};
  37.         execv("/bin/echo", argv);
  38.         exit(EXIT_FAILURE); // only if execv fails
  39.     }
  40.     close(filedes[1]);
  41.  
  42.     // at this point filedes[1] is open in child process to be written in
  43.     // and filedes[0] is open in parent process to be read from
  44.     char buffer[4096];
  45.     for (;;)
  46.     {
  47.         ssize_t count = read(filedes[0], buffer, sizeof(buffer));
  48.         if (count == -1)
  49.         {
  50.             if (errno == EINTR)
  51.             {
  52.                 continue;
  53.             }
  54.             else
  55.             {
  56.                 perror("read");
  57.                 exit(EXIT_FAILURE);
  58.             }
  59.         }
  60.         else if (count == 0)
  61.         {
  62.             break;
  63.         }
  64.         else
  65.         {
  66.             handle_child_process_output(buffer, count);
  67.         }
  68.     }
  69.     close(filedes[0]);
  70.     wait(NULL);
  71. }
  72.  
  73. void handle_child_process_output(char *buffer, ssize_t count)
  74. {
  75.     printf("%s", "\x1b[34m");
  76.     fwrite(buffer, count, sizeof(buffer[0]), stdout);
  77.     printf("%s", "\x1b[0m");
  78. }
Success #stdin #stdout 0s 4504KB
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Sphinx of black quartz, judge my vow.

https://ideone.com/OcqfBO
language:
C (gcc 8.3)
created:
4 years ago
visibility:
public

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