/*-------------------------------------------------------------------*/
/* testpipeparent2child.c                                            */
/* The pipe system call.                                             */
/*-------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <wait.h>

FILE *fdopen(int fildes, const char *mode);

#define BUFFER_LENGTH 100

static const char *pcProgramName = NULL;

void waitForChild(void)
{
   int iRet;
   iRet = wait(NULL);
   if (iRet == -1) perror(pcProgramName);
}

int main(int argc, char *argv[])
{
   int piPipeFd[2];
   FILE *psPipeWrite;
   int iPid;
   int iRet;

   pcProgramName = argv[0];

   iRet = pipe(piPipeFd);
   if (iRet == -1) {perror(pcProgramName); return 1; }

   fflush(NULL);
   iPid = fork();
   if (iPid == -1) {perror(pcProgramName); return 1; }

   if (iPid == 0)
   {
      FILE *psPipeRead;
      char pcBuffer[BUFFER_LENGTH];

      iRet = close(piPipeFd[1]);
      if (iRet == -1) {perror(pcProgramName); exit(1); }

      psPipeRead = fdopen(piPipeFd[0], "r");
      if (psPipeRead == NULL) {perror(pcProgramName); exit(1); }

      iRet = fscanf(psPipeRead, "%s", pcBuffer);
      if (iRet == EOF) {perror(pcProgramName); exit(1); }

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

      iRet = fclose(psPipeRead);
      if (iRet == EOF) {perror(pcProgramName); exit(1); }

      exit(0);
   }

   atexit(waitForChild);

   iRet = close(piPipeFd[0]);
   if (iRet == -1) {perror(pcProgramName); return 1; }

   psPipeWrite = fdopen(piPipeFd[1], "w");
   if (psPipeWrite == NULL) {perror(pcProgramName); return 1; }

   fprintf(psPipeWrite, "somedata\n");
   fflush(NULL);

   fclose(psPipeWrite);

   return 0;
}


/* Sample execution:

--> gcc -Wall -ansi -pedantic -o testpipeparent2child testpipeparent2child.c
--> testpipeparent2child
somedata
-->

*/