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];
                   pid_t 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);
             }



                           Copyright 1994 Novell, Inc.               Page 1

      p2open(3G)                                                p2open(3G)


      REFERENCES
            fclose(3S), popen(3S), setbuf(3S)

      RETURN VALUES
            A common problem is having too few file descriptors.  p2close
            returns -1 if the two file pointers are not from the same
            p2open.

      NOTICES
            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.






























                          Copyright 1994 Novell, Inc.               Page 2