p2open(3G)                                                       p2open(3G)


   NAME
         p2open, p2close - open, close pipes to and from a command

   SYNOPSIS
         cc [flag ...] file ...  -lgen [library ...]

         #include <libgen.h>

         int p2open (const char *cmd, FILE *fp[2]);
         int p2close (FILE *fp[2]);

   DESCRIPTION
         p2open forks and execs a shell running the command line pointed to by
         cmd.  On return, fp[0] points to a FILE pointer to write the
         command's standard input and fp[1] points to a FILE pointer to read
         from the command's standard output.  In this way the program has
         control over the input and output of the command.

         The function returns 0 if successful; otherwise it returns -1..

         p2close is used to close the file pointers that p2open opened.  It
         waits for the process to terminate and returns the process status.
         It returns 0 if successful; otherwise it returns -1..

   EXAMPLES
         #include    <stdio.h>
         #include    <libgen.h>
         main(argc,argv)
         int argc;
         char **argv;
         {
               FILE *fp[2];
               pidt pid;
               char buf[16];
               pid=p2open("/usr/bin/cat", fp);
               if ( pid == 0 ) {
                     fprintf(stderr, "p2open failed\n");
                     exit(1);
               }
               write(fileno(fp[0]),"This is a test\n", 16);
               if(read(fileno(fp[1]), buf, 16) <=0)
                     fprintf(stderr, "p2open failed\n");
               else
                     write(1, buf, 16);
               (void)p2close(fp);
         }

   DIAGNOSTICS
         A common problem is having too few file descriptors.




   8/91                                                                 Page 1

   p2open(3G)                                                       p2open(3G)


         p2close returns -1 if the two file pointers are not from the same
         p2open.

   NOTES
         Buffered writes on fp[0] can make it appear that the command is not
         listening.  Judiciously placed fflush calls or unbuffering fp[0] can
         be a big help; see fclose(3S).

         Many commands use buffered output when connected to a pipe.  That,
         too, can make it appear as if things are not working.

         Usage is not the same as for popen, although it is closely related.

   SEE ALSO
         fclose(3S), popen(3S), setbuf(3S).






































   Page 2                                                                 8/91