/*-------------------------------------------------------------------*/
/* testpipeforkexec.c                                                */
/* The pipe system call with fork and exec.                          */
/*-------------------------------------------------------------------*/

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

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

#define BUFFER_LENGTH 256

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 iPid;
   int iRet;
   int piPipeFd[2];
   FILE *psPipeRead;
   char pcBuffer[BUFFER_LENGTH];

   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)
   {
      char *ppcArgv[2];
      ppcArgv[0] = "date";
      ppcArgv[1] = NULL;

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

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

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

      execvp("date", ppcArgv);
      perror(pcProgramName);

      exit(1);
   }

   atexit(waitForChild);

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

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

   fgets(pcBuffer, BUFFER_LENGTH, psPipeRead);

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

   printf("%s", pcBuffer);

   return 0;
}


/* Sample execution:

--> gcc -Wall -ansi -pedantic -o testpipeforkexec testpipeforkexec.c
--> testpipeforkexec
Thu Jul 31 21:52:57 EDT 2003
-->

*/