--- /dev/null
+# extsprintf: extended POSIX-style sprintf
+
+Stripped down version of s[n]printf(3c). We make a best effort to throw an
+exception when given a format string we don't understand, rather than ignoring
+it, so that we won't break existing programs if/when we go implement the rest
+of this.
+
+This implementation currently supports specifying
+
+* field alignment ('-' flag),
+* zero-pad ('0' flag)
+* always show numeric sign ('+' flag),
+* field width
+* conversions for strings, decimal integers, and floats (numbers).
+* argument size specifiers. These are all accepted but ignored, since
+ Javascript has no notion of the physical size of an argument.
+
+Everything else is currently unsupported, most notably: precision, unsigned
+numbers, non-decimal numbers, and characters.
+
+Besides the usual POSIX conversions, this implementation supports:
+
+* `%j`: pretty-print a JSON object (using node's "inspect")
+* `%r`: pretty-print an Error object
+
+# Example
+
+First, install it:
+
+ # npm install extsprintf
+
+Now, use it:
+
+ var mod_extsprintf = require('extsprintf');
+ console.log(mod_extsprintf.sprintf('hello %25s', 'world'));
+
+outputs:
+
+ hello world