diff --git a/scsh/fdports1.c b/scsh/fdports1.c
index 9b73a82..3a44cd5 100644
--- a/scsh/fdports1.c
+++ b/scsh/fdports1.c
@@ -28,6 +28,7 @@
 #include "cstuff.h"
 #define NUM_FDPORTS 256
 #include "fdports.h"
+#include "machine/stdio_dep.h"
 
 /* Make sure our exports match up w/the implementation: */
 #include "fdports1.h"
diff --git a/scsh/select1.c b/scsh/select1.c
index 0cdeb42..b790ee2 100644
--- a/scsh/select1.c
+++ b/scsh/select1.c
@@ -16,6 +16,7 @@
 #include "cstuff.h"
 #include "fdports.h"	/* Accessors for Scheme I/O port internals. */
 #include "fdports1.h"	/* Import fdes2fstar(). */
+#include "machine/stdio_dep.h"	/* Import stdio buf-peeking ops. */
 
 /* Make sure our exports match up w/the implementation: */
 #include "select1.h"
@@ -29,29 +30,25 @@ extern FILE *fdes2fstar(int fd);
 static void or2_fdset(fd_set *x, fd_set *y, int max_elt);
 static int copyback_fdvec(scheme_value portvec, fd_set *fdset);
 
-/* RVEC, WVEC, and EVEC are Scheme vectors of integer file descriptors
-** and I/O ports. NSECS is an integer timeout value, or #f for infinite wait.
-** Do the select() call. Move every element we hit on to the front of
-** its vector. The number of hits are returned in R_NUMRDY, W_NUMRDY, and
-** E_NUMRDY. The principle return value is #f if we win, and a fixnum errno
-** value if we error out.
+/* RVEC, WVEC, and EVEC are Scheme vectors of integer file descriptors,
+** I/O ports, and #f's. NSECS is an integer timeout value, or #f for
+** infinite wait. Do the select() call, returning result fd_sets in the
+** passed pointers. Return 0 for OK, otherwise error is in errno.
 */
 
-scheme_value scm_select(scheme_value rvec, scheme_value wvec,
-			scheme_value evec, scheme_value nsecs,
-			int *r_numrdy, int *w_numrdy, int *e_numrdy)
+int do_select(scheme_value rvec, scheme_value wvec,
+	      scheme_value evec, scheme_value nsecs,
+	      fd_set *rset_ans, fd_set *wset_ans, fd_set *eset_ans)
 {
     struct timeval timeout, *tptr;
     fd_set rset_bufrdy, wset_bufrdy, eset_bufrdy;    /* Buffered port hits. */
-    fd_set rset_try,    wset_try,    eset_try;	     /* Real select() sets. */
     int rbuf_rdy=0, wbuf_rdy=0, bufrdy;	/* Set if we find buffered I/O hits. */
     int max_fd = -1;			/* Max fdes in the sets. */
     int nelts, i;
     int nfound;
 
-    FD_ZERO(&rset_try);		FD_ZERO(&wset_try);	FD_ZERO(&eset_try);
+    FD_ZERO(rset_ans);		FD_ZERO(wset_ans);	FD_ZERO(eset_ans);
     FD_ZERO(&rset_bufrdy);	FD_ZERO(&wset_bufrdy);	FD_ZERO(&eset_bufrdy);
-    *r_numrdy = *w_numrdy = *e_numrdy = 0;
 
     /* Scan the readvec elts. */
     nelts = VECTOR_LENGTH(rvec);
@@ -61,21 +58,21 @@ scheme_value scm_select(scheme_value rvec, scheme_value wvec,
 
 	if( FIXNUMP(elt) ) {			    /* It's an integer fdes. */
 	    fd = EXTRACT_FIXNUM(elt);
-	    FD_SET(fd, &rset_try);
+	    FD_SET(fd, rset_ans);
 	    }
 
-	else {					    /* It better be a port. */
+	else if( elt != SCHFALSE ) {		    /* It better be a port. */
 	    FILE *f;
 	    scheme_value data = *Port_PortData(elt);
 	    fd = EXTRACT_FIXNUM(*PortData_Fd(data));
 	    f = fdes2fstar(fd);
-	    if( !f ) return ENTER_FIXNUM(errno);
+	    if( !f ) return -1;
 	    else if( *PortData_Peek(data) != SCHFALSE /* Port has a peekchar */
 		     || !ibuf_empty(f) ) { 	     /* Stdio buf has chars. */
 		FD_SET(fd, &rset_bufrdy);
 		rbuf_rdy = 1; /* Hit. */
 		}
-	    else FD_SET(fd, &rset_try);		  /* No buffered data. */
+	    else FD_SET(fd, rset_ans);		  /* No buffered data. */
 	    }
 
 	max_fd = max(max_fd, fd);
@@ -89,19 +86,19 @@ scheme_value scm_select(scheme_value rvec, scheme_value wvec,
 
 	if( FIXNUMP(elt) ) {			    /* It's an integer fdes. */
 	    fd = EXTRACT_FIXNUM(elt);
-	    FD_SET(fd, &wset_try);
+	    FD_SET(fd, wset_ans);
 	    }
 
-	else {					    /* It better be a port. */
+	else if( elt != SCHFALSE ) {		    /* It better be a port. */
 	    FILE *f;
 	    fd = EXTRACT_FIXNUM(*PortFd(elt));
 	    f = fdes2fstar(fd);
-	    if( !f ) return ENTER_FIXNUM(errno);
+	    if( !f ) return -1;
 	    else if( !obuf_full(f) ) {		  /* I/O buf has room. */
 		FD_SET(fd, &wset_bufrdy);		
 		wbuf_rdy = 1; /* Hit. */
 		}
-	    else FD_SET(fd, &wset_try);		  /* No room. */
+	    else FD_SET(fd, wset_ans);		  /* No room. */
 	    }
 
 	max_fd = max(max_fd, fd);
@@ -115,12 +112,12 @@ scheme_value scm_select(scheme_value rvec, scheme_value wvec,
 
 	if( FIXNUMP(elt) ) {			/* It's an integer fdes. */
 	    fd = EXTRACT_FIXNUM(elt);
-	    FD_SET(fd, &rset_try);
+	    FD_SET(fd, rset_ans);
 	    }
 
-	else {					/* It better be a port. */
+	else if( elt != SCHFALSE ) {		    /* It better be a port. */
 	    fd = EXTRACT_FIXNUM(*PortFd(elt));
-	    FD_SET(fd, &rset_try);
+	    FD_SET(fd, rset_ans);
 	    }
 
 	max_fd = max(max_fd, fd);
@@ -139,30 +136,38 @@ scheme_value scm_select(scheme_value rvec, scheme_value wvec,
 	}
     else tptr = NULL;				/* #f => Infinite wait. */
 
-    nfound = select1(max_fd+1, &rset_try, &wset_try, &eset_try, tptr);/*Do it.*/
+    nfound = select1(max_fd+1, rset_ans, wset_ans, eset_ans, tptr); /* Do it.*/
 
     /* EINTR is not an error return if we have hits on buffered ports
     ** to report.
     */
     if( nfound < 0 )
-	if ( errno != EINTR || !bufrdy ) return ENTER_FIXNUM(errno);
+	if ( errno != EINTR || !bufrdy ) return -1;
 	else {	/* EINTR, but we have hits on buffered ports to report.  */
-	    FD_ZERO(&rset_try);		/* This should never happen --   */
-	    FD_ZERO(&wset_try);		/* EINTR on a zero-sec select()  */
-	    FD_ZERO(&eset_try);		/* -- but I'm paranoid.          */
+	    FD_ZERO(rset_ans);		/* This should never happen --   */
+	    FD_ZERO(wset_ans);		/* EINTR on a zero-sec select()  */
+	    FD_ZERO(eset_ans);		/* -- but I'm paranoid.          */
 	    }
 
     /* OR together the buffered-io ready sets and the fd ready sets. */
-    if( rbuf_rdy ) or2_fdset(&rset_try, &rset_bufrdy, max_fd);
-    if( wbuf_rdy ) or2_fdset(&wset_try, &wset_bufrdy, max_fd);
+    if( rbuf_rdy ) or2_fdset(rset_ans, &rset_bufrdy, max_fd);
+    if( wbuf_rdy ) or2_fdset(wset_ans, &wset_bufrdy, max_fd);
 
-    *r_numrdy = copyback_fdvec(rvec, &rset_try);
-    *w_numrdy = copyback_fdvec(wvec, &wset_try);
-    *e_numrdy = copyback_fdvec(evec, &eset_try);
-
-    return SCHFALSE;
+    return 0;
     }
 
+
+
+/* x = x or y */
+static void or2_fdset(fd_set *x, fd_set *y, int max_elt)
+{
+    int i;
+    for(i=max_elt+1; --i >= 0;)
+	if( FD_ISSET(i,y) ) FD_SET(i,x);
+    }
+
+
+
 /* PORTVEC is a vector of integer file descriptors and Scheme ports.
 ** Scan over the vector, and copy any elt whose file descriptor is in FDSET
 ** to the front of the vector. Return the number of elts thus copied.
@@ -184,10 +189,73 @@ static int copyback_fdvec(scheme_value portvec, fd_set *fdset)
     }
 
 
-/* x = x or y */
-static void or2_fdset(fd_set *x, fd_set *y, int max_elt)
+/* Overwrite every inactive element in the vector with #f;
+** Return count of active elements.
+*/
+
+static int clobber_inactives(scheme_value portvec, fd_set *fdset)
 {
-    int i;
-    for(i=max_elt+1; --i >= 0;)
-	if( FD_ISSET(i,y) ) FD_SET(i,x);
+    int count = 0;
+    int i = VECTOR_LENGTH(portvec);
+
+    while( --i >= 0 ) {
+	scheme_value elt = VECTOR_REF(portvec, i);
+	if( elt != SCHFALSE ) {
+	    int fd = EXTRACT_FIXNUM((FIXNUMP(elt)) ? elt : *PortFd(elt));
+	    if( FD_ISSET(fd,fdset) ) {
+		FD_CLR(fd,fdset); /* In case luser put elt in multiple times. */
+		++count;
+		}
+	    else VECTOR_REF(portvec, i) = SCHFALSE; /* Clobber. */
+	    }
+	}
+    return count;
+    }
+
+
+/* These two functions are the entry points to this file.
+*********************************************************
+*/
+
+/* Copy active elts back to the front of their vector;
+** Return error indicator & number of hits for each vector.
+*/
+
+scheme_value select_copyback(scheme_value rvec, scheme_value wvec,
+			     scheme_value evec, scheme_value nsecs,
+			     int *r_numrdy, int *w_numrdy, int *e_numrdy)
+{
+    fd_set rset, wset, eset;
+
+    if( do_select(rvec, wvec, evec, nsecs, &rset, &wset, &eset) ) {
+	*r_numrdy = *w_numrdy = *e_numrdy = 0;
+	return ENTER_FIXNUM(errno);
+	}
+    
+    *r_numrdy = copyback_fdvec(rvec, &rset);
+    *w_numrdy = copyback_fdvec(wvec, &wset);
+    *e_numrdy = copyback_fdvec(evec, &eset);
+    return SCHFALSE;
+    }
+
+
+/* Overwrite non-active elements in the vectors with #f;
+** return error indicator & number of hits for each vector.
+*/
+
+scheme_value select_filter(scheme_value rvec, scheme_value wvec,
+			   scheme_value evec, scheme_value nsecs,
+			   int *r_numrdy, int *w_numrdy, int *e_numrdy)
+{
+    fd_set rset, wset, eset;
+
+    if( do_select(rvec, wvec, evec, nsecs, &rset, &wset, &eset) ) {
+	*r_numrdy = *w_numrdy = *e_numrdy = 0;
+	return ENTER_FIXNUM(errno);
+	}
+    
+    *r_numrdy = clobber_inactives(rvec, &rset);
+    *w_numrdy = clobber_inactives(wvec, &wset);
+    *e_numrdy = clobber_inactives(evec, &eset);
+    return SCHFALSE;
     }
diff --git a/scsh/syscalls1.c b/scsh/syscalls1.c
index 945862c..4acb3df 100644
--- a/scsh/syscalls1.c
+++ b/scsh/syscalls1.c
@@ -22,6 +22,7 @@
 #include <utime.h>
 
 #include "cstuff.h"
+#include "machine/stdio_dep.h"
 
 /* Make sure our exports match up w/the implementation: */
 #include "syscalls1.h"
@@ -500,10 +501,11 @@ char *scm_gethostname(void)
 char *errno_msg(int i)
 {
   /* temp hack until we figure out what to do about losing sys_errlist's */
+extern
 #ifdef HAVE_CONST_SYS_ERRLIST
   const
 #endif
-    extern char *sys_errlist[]; 
+      char *sys_errlist[]; 
   extern int sys_nerr;
   return ( i < 0 || i > sys_nerr ) ? NULL		/* i.e., #f */
       				   : (char*) sys_errlist[i];