if.c

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        printf(" %*.*s",     -max_ip,    max_ip,    cur_if->ip);

        if (oflag) {
            printf(" %*s %*s", max_ibytes,  cur_if->s_ibytes,
                               max_obytes,  cur_if->s_obytes);
        } else {
            printf(" %*s %*s", max_ipkts,   cur_if->s_ipkts,
                               max_ierrs,   cur_if->s_ierrs);
            if (bflag) 
                printf(" %*s", max_ibytes,  cur_if->s_ibytes);
    
            printf(" %*s %*s", max_opkts,   cur_if->s_opkts,
                               max_oerrs,   cur_if->s_oerrs);
            if (bflag) 
                printf(" %*s", max_obytes,  cur_if->s_obytes);
            printf(" %*s",     max_outq,    cur_if->s_outq);
        }
     /* if (tflag)
            printf(" %4d", cur_if->???);
      */
        if (dflag)
            printf(" %4d", cur_if->drops);
        putchar('\n');
    }

        /*
         * ... and tidy up.
         */
    for (cur_if = if_head; cur_if; cur_if=if_head) {
        if_head=cur_if->next;
        cur_if->next = NULL;
        SNMP_FREE( cur_if );
    }
}


#define	MAXIF	100
struct	iftot {
	char	ift_name[128];		/* interface name */
        int     ifIndex;
	u_long	ift_ip;			/* input packets */
	u_long	ift_ib;			/* input bytes */
	u_long	ift_ie;			/* input errors */
	u_long	ift_op;			/* output packets */
	u_long	ift_ob;			/* output bytes */
	u_long	ift_oe;			/* output errors */
	u_long	ift_co;			/* collisions */
	u_long	ift_dr;			/* drops */
};

int signalled;	/* set if alarm goes off "early" */

/*
 * Print a running summary of interface statistics.
 * Repeat display every interval seconds, showing statistics
 * collected over that interval.  Assumes that interval is non-zero.
 * First line printed at top of screen is always cumulative.
 */
static void
sidewaysintpr(unsigned int interval)
{
    /*
     * As with the "one-shot" interface display, there are
     *   two different possible output formats.  The Net/
     *   Open-BSD style displays both information about a
     *   single interface *and* the overall totals.
     * The equivalent Free-BSD approach is to report on one
     *   or the other (rather than both).  This is probably
     *   more useful (IMO), and significantly more efficient.
     *   So that's the style implemented here.
     *
     * Note that the 'ifcol' OID buffer can represent a full
     *   instance (including ifIndex), rather than just a
     *   column object OID, as with the one-shot code.
     */
    oid    ifcol_oid[]  = { 1,3,6,1,2,1,2,2,1,0,0 };
    size_t ifcol_len    = OID_LENGTH( ifcol_oid );
    netsnmp_variable_list *var, *vp;
    struct iftot *ip  = NULL, *cur_if = NULL;    /* single I/F display */
    struct iftot *sum = NULL, *total  = NULL;    /* overall summary    */
    int    line;
    int    first;
    int    i;

    var = NULL;
    if ( intrface ) {
        /*
         * Locate the ifIndex of the interface to monitor,
         *   by walking the ifDescr column of the ifTable
         */
        ifcol_oid[ ifcol_len-2 ] = 2;   /* ifDescr  */
        snmp_varlist_add_variable( &var, ifcol_oid, ifcol_len-1,
                                   ASN_NULL, NULL,  0);
        i = strlen(intrface);
        netsnmp_query_walk( var, ss );
        for (vp=var; vp; vp=vp->next_variable) {
            if (strncmp(intrface, (char *)vp->val.string, i) == 0 &&
                i == vp->val_len)
                break;  /* found requested interface */
        }
        /*
         * XXX - Might be worth searching ifName/ifAlias as well
         */
        if (!vp) {
            fprintf(stderr, "%s: unknown interface\n", intrface );
            exit(1);
        }

        /*
         *  Prepare the current and previous 'iftot' structures,
         *    and set the ifIndex value in the OID buffer.
         */
        ip     = SNMP_MALLOC_TYPEDEF( struct iftot );
        cur_if = SNMP_MALLOC_TYPEDEF( struct iftot );
        if (!ip || !cur_if) {
            fprintf(stderr, "internal error\n");
            exit(1);
        }
        ifcol_oid[ ifcol_len-1 ] = vp->name[ ifcol_len-1 ];
        snmp_free_var( var );
        var = NULL;
    } else {
        /*
         *  Prepare the current and previous 'iftot' structures.
         *    (using different pointers, for consistency with *BSD code)
         */
        sum   = SNMP_MALLOC_TYPEDEF( struct iftot );
        total = SNMP_MALLOC_TYPEDEF( struct iftot );
        if (!sum || !total) {
            fprintf(stderr, "internal error\n");
            exit(1);
        }
    }

    timerSet( interval );
    first = 1;
banner:
    printf( "%17s %14s %16s", "input",
        intrface ? intrface : "(Total)", "output");
    putchar('\n');
    printf( "%10s %5s %10s %10s %5s %10s %5s",
        "packets", "errs", "bytes", "packets", "errs", "bytes", "colls");
    if (dflag)
	printf(" %5.5s", "drops");
    putchar('\n');
    fflush(stdout);
    line = 0;
loop:
    if ( intrface ) {
#define ADD_IFVAR( x ) ifcol_oid[ ifcol_len-2 ] = x; \
    snmp_varlist_add_variable( &var, ifcol_oid, ifcol_len, ASN_NULL, NULL,  0)
    /*  if (bflag) { */
            ADD_IFVAR( 10 );        /* ifInOctets     */
            ADD_IFVAR( 16 );        /* ifOutOctets    */
    /*  } */
        ADD_IFVAR( 11 );            /* ifInUcastPkts  */
        ADD_IFVAR( 12 );            /* ifInNUcastPkts */
        ADD_IFVAR( 14 );            /* ifInErrors     */
        ADD_IFVAR( 17 );            /* ifOutUcastPkts */
        ADD_IFVAR( 18 );            /* ifOutNUcastPkts */
        ADD_IFVAR( 20 );            /* ifOutErrors    */
        ADD_IFVAR( 21 );            /* ifOutQLen      */
        if (dflag) {
            ADD_IFVAR( 19 );        /* ifOutDiscards  */
        }
#undef ADD_IFVAR

        netsnmp_query_get( var, ss );   /* Or parallel walk ?? */
        cur_if->ift_ip = 0;
        cur_if->ift_ib = 0;
        cur_if->ift_ie = 0;
        cur_if->ift_op = 0;
        cur_if->ift_ob = 0;
        cur_if->ift_oe = 0;
        cur_if->ift_co = 0;
        cur_if->ift_dr = 0;
        cur_if->ifIndex = var->name[ ifcol_len-1 ];
        for (vp=var; vp; vp=vp->next_variable) {
            if ( ! vp->val.integer )
                continue;
            switch (vp->name[ifcol_len-2]) {
            case 10:    /* ifInOctets */
                cur_if->ift_ib = *vp->val.integer;
                break;
            case 11:    /* ifInUcastPkts */
                cur_if->ift_ip += *vp->val.integer;
                break;
            case 12:    /* ifInNUcastPkts */
                cur_if->ift_ip += *vp->val.integer;
                break;
            case 14:    /* ifInErrors */
                cur_if->ift_ie = *vp->val.integer;
                break;
            case 16:    /* ifOutOctets */
                cur_if->ift_ob = *vp->val.integer;
                break;
            case 17:    /* ifOutUcastPkts */
                cur_if->ift_op += *vp->val.integer;
                break;
            case 18:    /* ifOutNUcastPkts */
                cur_if->ift_op += *vp->val.integer;
                break;
            case 19:    /* ifOutDiscards */
                cur_if->ift_dr = *vp->val.integer;
                break;
            case 20:    /* ifOutErrors */
                cur_if->ift_oe = *vp->val.integer;
                break;
            case 21:    /* ifOutQLen */
                cur_if->ift_co = *vp->val.integer;
                break;
            }
        }
        snmp_free_varbind( var );
        var = NULL;
 
        if (!first) {
 	    printf("%10lu %5lu %10lu %10lu %5lu %10lu %5lu",
 		cur_if->ift_ip - ip->ift_ip,
 		cur_if->ift_ie - ip->ift_ie,
		cur_if->ift_ib - ip->ift_ib,
		cur_if->ift_op - ip->ift_op,
		cur_if->ift_oe - ip->ift_oe,
		cur_if->ift_ob - ip->ift_ob,
		cur_if->ift_co - ip->ift_co);
	    if (dflag)
		printf(" %5lu", cur_if->ift_dr - ip->ift_dr);
            putchar('\n');
            fflush(stdout);
	}
	ip->ift_ip = cur_if->ift_ip;
	ip->ift_ie = cur_if->ift_ie;
	ip->ift_ib = cur_if->ift_ib;
	ip->ift_op = cur_if->ift_op;
	ip->ift_oe = cur_if->ift_oe;
	ip->ift_ob = cur_if->ift_ob;
	ip->ift_co = cur_if->ift_co;
	ip->ift_dr = cur_if->ift_dr;
    }  /* (single) interface */
    else {
	sum->ift_ip = 0;
	sum->ift_ib = 0;
	sum->ift_ie = 0;
	sum->ift_op = 0;
	sum->ift_ob = 0;
	sum->ift_oe = 0;
	sum->ift_co = 0;
	sum->ift_dr = 0;
#define ADD_IFVAR( x ) ifcol_oid[ ifcol_len-2 ] = x; \
    snmp_varlist_add_variable( &var, ifcol_oid, ifcol_len-1, ASN_NULL, NULL,  0)
        ADD_IFVAR( 11 );            /* ifInUcastPkts  */
        ADD_IFVAR( 12 );            /* ifInNUcastPkts */
        ADD_IFVAR( 14 );            /* ifInErrors     */
        ADD_IFVAR( 17 );            /* ifOutUcastPkts */
        ADD_IFVAR( 18 );            /* ifOutNUcastPkts */
        ADD_IFVAR( 20 );            /* ifOutErrors    */
        ADD_IFVAR( 21 );            /* ifOutQLen      */
    /*  if (bflag) { */
            ADD_IFVAR( 10 );        /* ifInOctets     */
            ADD_IFVAR( 16 );        /* ifOutOctets    */
    /*  } */
        if (dflag) {
            ADD_IFVAR( 19 );        /* ifOutDiscards  */
        }
#undef ADD_IFVAR

        ifcol_oid[ ifcol_len-2 ] = 11;       /* ifInUcastPkts */
        while ( 1 ) {
            if (netsnmp_query_getnext( var, ss ) != SNMP_ERR_NOERROR)
                break;
            if ( snmp_oid_compare( ifcol_oid, ifcol_len-2,
                                   var->name, ifcol_len-2) != 0 )
                break;    /* End of Table */
            
            for ( vp=var; vp; vp=vp->next_variable ) {
                if ( ! vp->val.integer )
                    continue;
                switch ( vp->name[ ifcol_len-2 ] ) {
                case 10:    /* ifInOctets */
                    sum->ift_ib += *vp->val.integer;
                    break;
                case 11:    /* ifInUcastPkts */
                    sum->ift_ip += *vp->val.integer;
                    break;
                case 12:    /* ifInNUcastPkts */
                    sum->ift_ip += *vp->val.integer;
                    break;
                case 14:    /* ifInErrors */
                    sum->ift_ie += *vp->val.integer;
                    break;
                case 16:    /* ifOutOctets */
                    sum->ift_ob += *vp->val.integer;
                    break;
                case 17:    /* ifOutUcastPkts */
                    sum->ift_op += *vp->val.integer;
                    break;
                case 18:    /* ifOutNUcastPkts */
                    sum->ift_op += *vp->val.integer;
                    break;
                case 19:    /* ifOutDiscards */
                    sum->ift_dr += *vp->val.integer;
                    break;
                case 20:    /* ifOutErrors */
                    sum->ift_oe += *vp->val.integer;
                    break;
                case 21:    /* ifOutQLen */
                    sum->ift_co += *vp->val.integer;
                    break;
                }
            }
            /*
             * Now loop to retrieve the next entry from the table.
             */
        }   /* while (1) */

        snmp_free_varbind( var );
        var = NULL;
 
        if (!first) {
 	    printf("%10lu %5lu %10lu %10lu %5lu %10lu %5lu",
 		sum->ift_ip - total->ift_ip,
 		sum->ift_ie - total->ift_ie,
		sum->ift_ib - total->ift_ib,
		sum->ift_op - total->ift_op,
		sum->ift_oe - total->ift_oe,
		sum->ift_ob - total->ift_ob,
		sum->ift_co - total->ift_co);
	    if (dflag)
		printf(" %5lu", sum->ift_dr - total->ift_dr);
            putchar('\n');
            fflush(stdout);
	}
	total->ift_ip = sum->ift_ip;
	total->ift_ie = sum->ift_ie;
	total->ift_ib = sum->ift_ib;
	total->ift_op = sum->ift_op;
	total->ift_oe = sum->ift_oe;
	total->ift_ob = sum->ift_ob;
	total->ift_co = sum->ift_co;
	total->ift_dr = sum->ift_dr;
    }  /* overall summary */

    timerPause();
    timerSet(interval);
    line++;
    first = 0;
    if (line == 21)
    	goto banner;
    else
    	goto loop;
    /*NOTREACHED*/
}


/*
 * timerSet sets or resets the timer to fire in "interval" seconds.
 * timerPause waits only if the timer has not fired.
 * timing precision is not considered important.
 */

#if (defined(WIN32) || defined(cygwin))
static int      sav_int;
static time_t   timezup;
static void
timerSet(int interval_seconds)
{
    sav_int = interval_seconds;
    timezup = time(0) + interval_seconds;
}

/*
 * you can do better than this ! 
 */
static void
timerPause(void)
{
    time_t          now;
    while (time(&now) < timezup)
#ifdef WIN32
        Sleep(400);
#else
    {
        struct timeval  tx;
        tx.tv_sec = 0;
        tx.tv_usec = 400 * 1000;        /* 400 milliseconds */
        select(0, 0, 0, 0, &tx);
    }
#endif
}

#else

/*
 * Called if an interval expires before sidewaysintpr has completed a loop.
 * Sets a flag to not wait for the alarm.
 */
RETSIGTYPE
catchalarm(int sig)
{
    signalled = YES;
}

static void
timerSet(int interval_seconds)
{
#ifdef HAVE_SIGSET
    (void) sigset(SIGALRM, catchalarm);
#else
    (void) signal(SIGALRM, catchalarm);
#endif
    signalled = NO;
    (void) alarm(interval_seconds);
}

static void
timerPause(void)
{
#ifdef HAVE_SIGHOLD
    sighold(SIGALRM);
    if (!signalled) {
        sigpause(SIGALRM);
    }
#else
    int             oldmask;
    oldmask = sigblock(sigmask(SIGALRM));
    if (!signalled) {
        sigpause(0);
    }
    sigsetmask(oldmask);
#endif
}

#endif                          /* !WIN32 && !cygwin */