From owner-freebsd-hackers  Sun May 30 23:44:21 1999
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Date: Sun, 30 May 1999 23:44:16 -0700 (PDT)
From: Julian Elischer <julian@whistle.com>
To: hackers@freebsd.org
Subject: sio driver and select puzzle.
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The following code is SUPPOSED to return to me when a 
character is available for reading..

but it doesn't.

any one care to point out the obvious bug?

main()
{
        int filedes;
        struct termios newterm;
        struct termios oldterm;
        int     child;
        int     retval;
        struct perchild *cp;
        int sel_nfds;

        filedes = open("/dev/cuaa1", O_RDWR, 0);
        if (filedes == -1)
                err(1,"cant open cuaa1");
        retval = tcgetattr(filedes, &oldterm);
        if ( retval == -1)
                err(1, " can't get termios");
        newterm = oldterm;
        newterm.c_cflag = CLOCAL | CREAD | CS8;
        newterm.c_oflag = OPOST | ONLCR;
        newterm.c_iflag = 0;
        newterm.c_lflag = 0;
        newterm.c_ispeed = B57600;
        newterm.c_ospeed = B57600;
        newterm.c_cc[VMIN] = 1;
        newterm.c_cc[VTIME] = 0;

        retval = tcsetattr(filedes, TCSAFLUSH, &newterm);
        if ( retval == -1)
                err(1, " can't set termios");


        /*
         * get role             
         */                             
        for(;;) {                       
                sprintf(linebuf2, "%20s\n","1= test, 2=target");
                write(filedes, linebuf2, strlen(linebuf2));
                sprintf(linebuf2, "%20s\n","9= quit and reboot");
                write(filedes, linebuf2, strlen(linebuf2));
                sel_nfds = 0;
                FD_ZERO(&read_set);      
                FD_SET( filedes, &read_set);
                if (filedes > sel_nfds)
                sel_nfds = filedes;
                        

                printf("select called %d\n",sel_nfds);
                sel_nfds = select(sel_nfds, &read_set, NULL, NULL, NULL);
                printf("select returned %d\n",sel_nfds);

[...]


the program gets to "select called %d"
 but when I send  a character down the line
it doesn't return from  the select.


this is in 3.1 (approximatly)

If I comment out the select, the read that follows it (not shown) does get
the character. 

julian




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