diff --git a/CHANGES b/CHANGES
index 7a5431d..b33903a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,7 @@
 0.20:
   add errmsg API
   work around broken Linux sendfile API (offset 64-bit but count 32-bit)
+  add io_appendfile, io_readwritefile
 
 0.19.2:
   for some reason, a botched dependency slipped in the the Makefile
diff --git a/Makefile b/Makefile
index db6b591..50ab4d7 100644
--- a/Makefile
+++ b/Makefile
@@ -162,6 +162,9 @@ fmt_ulong0.o: fmt/fmt_ulong0.c ./fmt.h
 fmt_ulonglong.o: fmt/fmt_ulonglong.c ./fmt.h
 fmt_xlong.o: fmt/fmt_xlong.c ./fmt.h ./haveinline.h
 fmt_xlonglong.o: fmt/fmt_xlonglong.c ./fmt.h
+io_appendfile.o: io/io_appendfile.c ./io_internal.h ./io.h ./uint64.h \
+  ./taia.h ./tai.h ./array.h ./haveepoll.h ./havekqueue.h ./havedevpoll.h \
+  ./havesigio.h
 io_canread.o: io/io_canread.c ./io_internal.h ./io.h ./uint64.h ./taia.h \
   ./tai.h ./array.h ./haveepoll.h ./havekqueue.h ./havedevpoll.h \
   ./havesigio.h
@@ -210,6 +213,9 @@ io_pipe.o: io/io_pipe.c ./io_internal.h ./io.h ./uint64.h ./taia.h \
 io_readfile.o: io/io_readfile.c ./io_internal.h ./io.h ./uint64.h \
   ./taia.h ./tai.h ./array.h ./haveepoll.h ./havekqueue.h ./havedevpoll.h \
   ./havesigio.h
+io_readwritefile.o: io/io_readwritefile.c ./io_internal.h ./io.h \
+  ./uint64.h ./taia.h ./tai.h ./array.h ./haveepoll.h ./havekqueue.h \
+  ./havedevpoll.h ./havesigio.h
 io_receivefd.o: io/io_receivefd.c ./io_internal.h ./io.h ./uint64.h \
   ./taia.h ./tai.h ./array.h ./haveepoll.h ./havekqueue.h ./havedevpoll.h \
   ./havesigio.h
@@ -584,7 +590,7 @@ DNS_OBJS=dns_dfd.o dns_domain.o dns_dtda.o dns_ip.o dns_ip6.o dns_ipq.o dns_ipq6
 CASE_OBJS=case_diffb.o case_diffs.o case_lowerb.o case_lowers.o case_starts.o 
 MULT_OBJS=imult16.o imult32.o imult64.o umult16.o umult32.o umult64.o 
 ARRAY_OBJS=array_allocate.o array_bytes.o array_cat.o array_cat0.o array_catb.o array_cate.o array_cats.o array_cats0.o array_equal.o array_fail.o array_get.o array_length.o array_reset.o array_start.o array_trunc.o array_truncate.o 
-IO_OBJS=io_canread.o io_canwrite.o io_check.o io_close.o io_closeonexec.o io_createfile.o io_dontwantread.o io_dontwantwrite.o io_eagain.o io_fd.o io_finishandshutdown.o io_getcookie.o io_nonblock.o io_passfd.o io_pipe.o io_readfile.o io_receivefd.o io_sendfile.o io_setcookie.o io_sigpipe.o io_socketpair.o io_timeout.o io_timeouted.o io_tryread.o io_tryreadtimeout.o io_trywrite.o io_trywritetimeout.o io_wait.o io_waitread.o io_waituntil.o io_waituntil2.o io_waitwrite.o io_wantread.o io_wantwrite.o iob_addbuf.o iob_addbuf_free.o iob_addbuf_internal.o iob_addfile.o iob_addfile_close.o iob_adds.o iob_adds_free.o iob_new.o iob_prefetch.o iob_reset.o iob_send.o 
+IO_OBJS=io_appendfile.o io_canread.o io_canwrite.o io_check.o io_close.o io_closeonexec.o io_createfile.o io_dontwantread.o io_dontwantwrite.o io_eagain.o io_fd.o io_finishandshutdown.o io_getcookie.o io_nonblock.o io_passfd.o io_pipe.o io_readfile.o io_readwritefile.o io_receivefd.o io_sendfile.o io_setcookie.o io_sigpipe.o io_socketpair.o io_timeout.o io_timeouted.o io_tryread.o io_tryreadtimeout.o io_trywrite.o io_trywritetimeout.o io_wait.o io_waitread.o io_waituntil.o io_waituntil2.o io_waitwrite.o io_wantread.o io_wantwrite.o iob_addbuf.o iob_addbuf_free.o iob_addbuf_internal.o iob_addfile.o iob_addfile_close.o iob_adds.o iob_adds_free.o iob_new.o iob_prefetch.o iob_reset.o iob_send.o 
 TEXTCODE_OBJS=base64.o fmt_base64.o fmt_cescape.o fmt_foldwhitespace.o fmt_hexdump.o fmt_html.o fmt_quotedprintable.o fmt_to_array.o fmt_to_sa.o fmt_tofrom_array.o fmt_urlencoded.o fmt_uuencoded.o fmt_yenc.o scan_base64.o scan_cescape.o scan_hexdump.o scan_html.o scan_quotedprintable.o scan_to_array.o scan_to_sa.o scan_tofrom_array.o scan_urlencoded.o scan_uuencoded.o scan_yenc.o 
 
 byte.a: $(BYTE_OBJS)
diff --git a/io.h b/io.h
index 8e84296..5f3f052 100644
--- a/io.h
+++ b/io.h
@@ -12,6 +12,12 @@ int io_readfile(int64* d,const char* s);
 /* like open(s,O_WRONLY|O_CREAT|O_TRUNC,0600) */
 /* return 1 if ok, 0 on error */
 int io_createfile(int64* d,const char* s);
+/* like open(s,O_RDWR) */
+/* return 1 if ok, 0 on error */
+int io_readwritefile(int64* d,const char* s);
+/* like open(s,O_WRONLY|O_APPEND|O_CREAT,0600) */
+/* return 1 if ok, 0 on error */
+int io_appendfile(int64* d,const char* s);
 /* like pipe(d) */
 /* return 1 if ok, 0 on error */
 int io_pipe(int64* d);
diff --git a/io/io_appendfile.3 b/io/io_appendfile.3
new file mode 100644
index 0000000..f29a44c
--- /dev/null
+++ b/io/io_appendfile.3
@@ -0,0 +1,16 @@
+.TH io_appendfile 3
+.SH NAME
+io_appendfile \- open a file for appending
+.SH SYNTAX
+.B #include <io.h>
+
+int \fBio_appendfile\fP(int64* d,const char* s);
+.SH DESCRIPTION
+io_appendfile sets d to the number of a new descriptor writing to the
+end of the disk file named \fIs\fR, and returns 1.  If the file does not
+exist, it will be created with mode 0600.
+
+If something goes wrong, io_appendfile sets \fIerrno\fR to indicate the error, and
+returns 0; it does not create a new descriptor, and it does not touch d.
+.SH "SEE ALSO"
+io_readfile(3), io_createfile(3), io_readwritefile(3)
diff --git a/io/io_appendfile.c b/io/io_appendfile.c
new file mode 100644
index 0000000..bdc4c42
--- /dev/null
+++ b/io/io_appendfile.c
@@ -0,0 +1,13 @@
+#define _FILE_OFFSET_BITS 64
+#include <unistd.h>
+#include <fcntl.h>
+#include "io_internal.h"
+
+int io_appendfile(int64* d,const char* s) {
+  long fd=open(s,O_WRONLY|O_APPEND|O_CREAT,0600);
+  if (fd != -1) {
+    *d=fd;
+    return 1;
+  }
+  return 0;
+}
diff --git a/io/io_createfile.3 b/io/io_createfile.3
index 9267935..958f838 100644
--- a/io/io_createfile.3
+++ b/io/io_createfile.3
@@ -14,4 +14,4 @@ If something goes wrong, io_createfile sets \fIerrno\fR to indicate the error, a
 returns 0; it does not create a new descriptor, and it does not touch d.
 (However, it may have truncated or created the file.)
 .SH "SEE ALSO"
-io_readfile(3)
+io_readfile(3), io_appendfile(3), io_readwritefile(3)
diff --git a/io/io_readfile.3 b/io/io_readfile.3
index 37a69e8..a858a9f 100644
--- a/io/io_readfile.3
+++ b/io/io_readfile.3
@@ -12,4 +12,4 @@ disk file named \fIs\fR, and returns 1.
 If something goes wrong, io_readfile sets \fIerrno\fR to indicate the error, and
 returns 0; it does not create a new descriptor, and it does not touch d.
 .SH "SEE ALSO"
-io_readfile(3)
+io_createfilefile(3), io_appendfile(3), io_readwritefile(3)
diff --git a/io/io_readwritefile.3 b/io/io_readwritefile.3
new file mode 100644
index 0000000..57cd017
--- /dev/null
+++ b/io/io_readwritefile.3
@@ -0,0 +1,16 @@
+.TH io_readwritefile 3
+.SH NAME
+io_readfile \- open a file for reading and writing
+.SH SYNTAX
+.B #include <io.h>
+
+int \fBio_readwritefile\fP(int64* d,const char* s);
+.SH DESCRIPTION
+io_readwritefile sets d to the number of a new descriptor reading from
+and writing to the disk file named \fIs\fR, and returns 1.  The file
+needs to exist.
+
+If something goes wrong, io_readwritefile sets \fIerrno\fR to indicate the error, and
+returns 0; it does not create a new descriptor, and it does not touch d.
+.SH "SEE ALSO"
+io_readfile(3), io_createfile(3), io_appendfile(3)
diff --git a/io/io_readwritefile.c b/io/io_readwritefile.c
new file mode 100644
index 0000000..b7d9606
--- /dev/null
+++ b/io/io_readwritefile.c
@@ -0,0 +1,13 @@
+#define _FILE_OFFSET_BITS 64
+#include <unistd.h>
+#include <fcntl.h>
+#include "io_internal.h"
+
+int io_readwritefile(int64* d,const char* s) {
+  long fd=open(s,O_RDWR);
+  if (fd != -1) {
+    *d=fd;
+    return 1;
+  }
+  return 0;
+}