#ifndef __LINK_H__
#define __LINK_H__

/*  link.h  
*  
*   Link  module allows a program to form links to other separately
*   executing programs  and communicate with them. Links can be
*   opened and closed, and the program using this library can 
*   writeto and read from the other  program over the link.  
*
*/

typedef struct _link_handle  /* holds all info relevant to one link. */
{
  int pipefd1[2], pipefd2[2];
  int pid;
  FILE   *fpin,  *fpout;
} link_handle;

void link_open(link_handle *l, char name[], char param[]);
void link_open2(link_handle *l, char name[], const char *params[]);
void link_close(link_handle *l);

/*  Close the link to a program  that has terminated. Use link_kill
    if the program needs to be terminated as well  */

int link_read(link_handle *l, char s[]);
/*  read from the program started with link_open. Returns a 0 if
    there was stuff to read, or a 1 if the linked program terminated.  */

int link_input_waiting(link_handle *l);
/*  Returns the number of bytes waiting in the input buffer.  If
   0, then link_read will  block if it is called.  */

void link_write(link_handle *l, char s[]);
/* write a string to the program, with a newline.   */

void link_kill(link_handle *);

/*  kill the program and close the link.  If the program has terminated
  on its own use link_close instead.  */

#endif /* __LINK_H__ */