[Fwd: Re: dangerous stuff popen2()]

[Kim Holburn]

Here's one I wrote/adapted ages ago.  Two files ppipe.h and ppipe.c

ppipe.h:
------------------------------------------------
/* @(#)ppipe.h  1.2     97/09/19 (12:20:14) */

int ppopen(FILE **IN, FILE **OUT, char *shcmd, int *pid);
int ppclose(int pid);

/*
  create pipe that my program can output to and input from
  Used in this order :

  FILE *IN, *OUT;
  int pid;

  if (ppopen (&IN, &OUT, "shell command", &pid)!=0) don't do it;
  fprintf (OUT, "things");
  fclose (OUT);
  fgets (IN etc
  fclose (IN);
  ppclose(pid)
 */
------------------------------------------------
ppipe.c
------------------------------------------------
/* ppipe.c */

/* @(#)ppipe.c  1.1     97/09/19 (12:15:38) */

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

/*

      parent                  child
      ------                  -----

     pfd1[1]       --->      pfd1[0]
  close pfd1[0]           close pfd1[1]
                                |
                                v
                             system
                                |
                                v
     pfd2[0]       <---      pfd2[1]
  close pfd2[1]           close pfd2[0]

*/

int ppopen(FILE **IN, FILE **OUT, char *shcmd, int *pid)
{
  static int pfd1[2];    /* pipe, from parent to child */
  static int pfd2[2];    /* pipe, from child to parent */

  /*
   * create a pipe, generally speak, a pipe is a half-duplex
   * communication channel (except SVR4)
   */
  if (pipe(pfd1) < 0) {
    perror("pipe one creation");
    return 1;
  }
  if (pipe(pfd2) < 0) {
    perror("pipe two creation");
    return 2;
  }

  /*
   * fork a child process
   */
  if ((*pid=fork()) <0 ) {
    perror("fork child");
    return 3;
  }

  /*
   * the shell command get executed by the child process
   */
  if (*pid == 0) {
    /*
     * redirect the standard input and output 
     */
    dup2(pfd1[0], 0);
    dup2(pfd2[1], 1);
    close(pfd1[1]);
    close(pfd2[0]);

    /*
     * execute the shell command, the output goes to the pipe
     */
    system(shcmd);

    exit(0);
  } /* child process */


  /*
   * in the parent process, pfd1[1] and pfd2[0] is useless
   */
  close(pfd1[0]);
  close(pfd2[1]);

  /*
   * pipe data into the child process
   */
  *OUT=fdopen (pfd1[1], "w");

  /*
   * read data from the child process
   */
  *IN=fdopen (pfd2[0], "r");
  return 0;
}

int ppclose (int pid)
{
  int status;    /* exit status of child process */

  waitpid(pid, &status, 0);
  return(status);
}
--------------------------------------------------------


-- 
--
Kim Holburn  Network Consultant  P/F: +61 2 61258620 M: +61 0417820641
Email: kim.holburn at anu.edu.au - PGP Public Key on request

Life is complex - It has real and imaginary parts.
     Andrea Leistra (rec.arts.sf.written.Robert-jordan)