diff --git a/fmt.h b/fmt.h
index 88b4580..7a61af0 100644
--- a/fmt.h
+++ b/fmt.h
@@ -65,9 +65,9 @@ unsigned int fmt_strn(char *dest,const char *src,unsigned int limit) __THROW;
 unsigned int fmt_pad(char* dest,const char* src,unsigned int srclen,unsigned int padlen,unsigned int maxlen) __THROW;
 
 /* "foo" -> "foo  "
- * write padlen-srclen spaces, if that is >= 0.  Then copy srclen
- * characters from src.  Truncate only if total length is larger than
- * maxlen.  Return number of characters written. */
-unsigned int fmt_fill(char* dest,const char* src,unsigned int srclen,unsigned int padlen,unsigned int maxlen) __THROW;
+ * append padlen-srclen spaces after dest, if that is >= 0.  Truncate
+ * only if total length is larger than maxlen.  Return number of
+ * characters written. */
+unsigned int fmt_fill(char* dest,unsigned int srclen,unsigned int padlen,unsigned int maxlen) __THROW;
 
 #endif
diff --git a/fmt/fmt_fill.3 b/fmt/fmt_fill.3
new file mode 100644
index 0000000..e059afb
--- /dev/null
+++ b/fmt/fmt_fill.3
@@ -0,0 +1,22 @@
+.TH fmt_fill 3
+.SH NAME
+fmt_fill \- append spaces to a string
+.SH SYNTAX
+.B #include <fmt.h>
+
+unsigned int \fBfmt_fill\fP(char *\fIdest\fR,
+      unsigned int \fIsrclen\fR, unsigned int \fIpadlen\fR,
+      unsigned int \fImaxlen\fR);
+.SH DESCRIPTION
+fmt_fill appends \fIpadlen\fR-\fIsrclen\fR spaces (if that number is
+positive) to \fIdest\fR (which holds \fIsrclen\fR bytes).  It truncates
+the output only if the length would exceed \fImaxlen\fR.
+
+It returns the number of bytes it wrote.
+
+fmt_fill does not append \\0.
+
+If \fIdest\fR equals FMT_LEN (i.e. is zero), fmt_fill returns the number
+of bytes it would have written.
+.SH "SEE ALSO"
+fmt_strn(3), fmt_pad(3)
diff --git a/fmt/fmt_fill.c b/fmt/fmt_fill.c
index 5c90f86..9f63e88 100644
--- a/fmt/fmt_fill.c
+++ b/fmt/fmt_fill.c
@@ -1,17 +1,18 @@
 #include "fmt.h"
 
 /* "foo" -> "foo  "
- *  Copy srclen characters from src.  write padlen-srclen spaces, if
- *  that is >= 0.  Truncate only if total length is larger than maxlen.
- *  Return number of characters written. */
-unsigned int fmt_fill(char* dest,const char* src,unsigned int srclen,unsigned int padlen,unsigned int maxlen) {
+ * append padlen-srclen spaces after dest, if that is >= 0.  Truncate
+ * only if total length is larger than maxlen.  Return number of
+ * characters written. */
+unsigned int fmt_fill(char* dest,unsigned int srclen,unsigned int padlen,unsigned int maxlen) {
   int todo;
   char* olddest=dest;
   char* max=dest+maxlen;
-  for (todo=srclen; todo>0; --todo) {
-    if (dest>max) break;
-    *dest=*src; ++dest; ++src;
+  if (dest==0) {
+    int sum=srclen>padlen?srclen:padlen;
+    return sum>maxlen?maxlen:sum;
   }
+  dest+=srclen;
   for (todo=padlen-srclen; todo>0; --todo) {
     if (dest>max) break;
     *dest=' '; ++dest;
diff --git a/fmt/fmt_pad.3 b/fmt/fmt_pad.3
new file mode 100644
index 0000000..934ae82
--- /dev/null
+++ b/fmt/fmt_pad.3
@@ -0,0 +1,22 @@
+.TH fmt_pad 3
+.SH NAME
+fmt_pad \- pad a string with spaces.
+.SH SYNTAX
+.B #include <fmt.h>
+
+unsigned int \fBfmt_pad\fP(char *\fIdest\fR, const char *\fIsource\fR,
+      unsigned int \fIsrclen\fR, unsigned int \fIpadlen\fR,
+      unsigned int \fImaxlen\fR);
+.SH DESCRIPTION
+fmt_pad writes \fIpadlen\fR-\fIsrclen\fR spaces (if that number is
+positive) and then \fIsrclen\fR characters from \fIsource\fR.  It
+truncates the output only if the length would exceed \fImaxlen\fR.
+
+It returns the number of bytes it wrote.
+
+fmt_pad does not append \\0.
+
+If \fIdest\fR equals FMT_LEN (i.e. is zero), fmt_pad returns the number
+of bytes it would have written.
+.SH "SEE ALSO"
+fmt_strn(3), fmt_fill(3)
diff --git a/fmt/fmt_pad.c b/fmt/fmt_pad.c
index 90a02fa..7b56285 100644
--- a/fmt/fmt_pad.c
+++ b/fmt/fmt_pad.c
@@ -8,7 +8,12 @@ unsigned int fmt_pad(char* dest,const char* src,unsigned int srclen,unsigned int
   int todo;
   char* olddest=dest;
   char* max=dest+maxlen;
-  for (todo=padlen-srclen; todo>0; --todo) {
+  todo=padlen-srclen;
+  if (dest==0) {
+    int sum=srclen>padlen?srclen:padlen;
+    return sum>maxlen?maxlen:sum;
+  }
+  for (; todo>0; --todo) {
     if (dest>max) break;
     *dest=' '; ++dest;
   }
diff --git a/fmt/fmt_strn.3 b/fmt/fmt_strn.3
index 1e53260..277f3da 100644
--- a/fmt/fmt_strn.3
+++ b/fmt/fmt_strn.3
@@ -1,6 +1,6 @@
 .TH fmt_strn 3
 .SH NAME
-fmt_str \- write an ASCII string
+fmt_strn \- write an ASCII string
 .SH SYNTAX
 .B #include <fmt.h>
 
diff --git a/t.c b/t.c
index 2e34438..4a6e572 100644
--- a/t.c
+++ b/t.c
@@ -15,7 +15,8 @@
 
 int main(int argc,char* argv[]) {
   char buf[100];
-  buf[fmt_fill(buf,"foobarbaz",3,5,100)]=0;
+  strcpy(buf,"foobarbaz");
+  buf[fmt_fill(buf,3,5,100)]=0;
   printf("\"%s\"\n",buf);
 #if 0
   unsigned long len;