Tribblix: manual page: xmlwf.1

XMLWF(1) XMLWF(1)

NAME

xmlwf - Determines if an XML document is well-formed

SYNOPSIS

xmlwf
[OPTIONS] [FILE ...]
xmlwf
-h | --help
xmlwf
-v | --version

DESCRIPTION

xmlwf uses the Expat library to determine if an XML document is well-
formed. It is non-validating.

If you do not specify any files on the command-line, and you have a
recent version of xmlwf, the input file will be read from standard
input.

WELL-FORMED DOCUMENTS
A well-formed document must adhere to the following rules:

+o The file begins with an XML declaration. For instance, <?xml
version="1.0" standalone="yes"?>. NOTE: xmlwf does not currently
check for a valid XML declaration.

+o Every start tag is either empty (<tag/>) or has a corresponding end
tag.

+o There is exactly one root element. This element must contain all
other elements in the document. Only comments, white space, and
processing instructions may come after the close of the root
element.

+o All elements nest properly.

+o All attribute values are enclosed in quotes (either single or
double).

If the document has a DTD, and it strictly complies with that DTD,
then the document is also considered valid. xmlwf is a non-
validating parser -- it does not check the DTD. However, it does
support external entities (see the -x option).

OPTIONS

When an option includes an argument, you may specify the argument
either separately ("-d output") or concatenated with the option
("-doutput"). xmlwf supports both.

-a factor
Sets the maximum tolerated amplification factor for protection
against billion laughs attacks (default: 100.0). The
amplification factor is calculated as ..

amplification := (direct + indirect) / direct

.. while parsing, whereas <direct> is the number of bytes read
from the primary document in parsing and <indirect> is the
number of bytes added by expanding entities and reading of
external DTD files, combined.

NOTE: If you ever need to increase this value for non-attack
payload, please file a bug report.

-b bytes
Sets the number of output bytes (including amplification)
needed to activate protection against billion laughs attacks
(default: 8 MiB). This can be thought of as an "activation
threshold".

NOTE: If you ever need to increase this value for non-attack
payload, please file a bug report.

-c If the input file is well-formed and xmlwf doesn't encounter
any errors, the input file is simply copied to the output
directory unchanged. This implies no namespaces (turns off
-n) and requires -d to specify an output directory.

-d output-dir
Specifies a directory to contain transformed representations
of the input files. By default, -d outputs a canonical
representation (described below). You can select different
output formats using -c, -m and -N.

The output filenames will be exactly the same as the input
filenames or "STDIN" if the input is coming from standard
input. Therefore, you must be careful that the output file
does not go into the same directory as the input file.
Otherwise, xmlwf will delete the input file before it
generates the output file (just like running cat < file > file
in most shells).

Two structurally equivalent XML documents have a byte-for-byte
identical canonical XML representation. Note that ignorable
white space is considered significant and is treated
equivalently to data. More on canonical XML can be found at
http://www.jclark.com/xml/canonxml.html .

-e encoding
Specifies the character encoding for the document, overriding
any document encoding declaration. xmlwf supports four built-
in encodings: US-ASCII, UTF-8, UTF-16, and ISO-8859-1. Also
see the -w option.

-g bytes
Sets the buffer size to request per call pair to XML_GetBuffer
and read (default: 8 KiB).

-h, --help
Prints short usage information on command xmlwf, and then
exits. Similar to this man page but more concise.

-k When processing multiple files, xmlwf by default halts after
the the first file with an error. This tells xmlwf to report
the error but to keep processing. This can be useful, for
example, when testing a filter that converts many files to XML
and you want to quickly find out which conversions failed.

-m Outputs some strange sort of XML file that completely
describes the input file, including character positions.
Requires -d to specify an output file.

-n Turns on namespace processing. (describe namespaces) -c
disables namespaces.

-N Adds a doctype and notation declarations to canonical XML
output. This matches the example output used by the formal
XML test cases. Requires -d to specify an output file.

-p Tells xmlwf to process external DTDs and parameter entities.

Normally xmlwf never parses parameter entities. -p tells it to
always parse them. -p implies -x.

-q Disable reparse deferral, and allow quadratic parse runtime on
large tokens (default: reparse deferral enabled).

-r Normally xmlwf memory-maps the XML file before parsing; this
can result in faster parsing on many platforms. -r turns off
memory-mapping and uses normal file IO calls instead. Of
course, memory-mapping is automatically turned off when
reading from standard input.

Use of memory-mapping can cause some platforms to report
substantially higher memory usage for xmlwf, but this appears
to be a matter of the operating system reporting memory in a
strange way; there is not a leak in xmlwf.

-s Prints an error if the document is not standalone. A document
is standalone if it has no external subset and no references
to parameter entities.

-t Turns on timings. This tells Expat to parse the entire file,
but not perform any processing. This gives a fairly accurate
idea of the raw speed of Expat itself without client overhead.
-t turns off most of the output options (-d, -m, -c, ...).

-v, --version
Prints the version of the Expat library being used, including
some information on the compile-time configuration of the
library, and then exits.

-w Enables support for Windows code pages. Normally, xmlwf will
throw an error if it runs across an encoding that it is not
equipped to handle itself. With -w, xmlwf will try to use a
Windows code page. See also -e.

-x Turns on parsing external entities.

Non-validating parsers are not required to resolve external
entities, or even expand entities at all. Expat always
expands internal entities (?), but external entity parsing
must be enabled explicitly.

External entities are simply entities that obtain their data
from outside the XML file currently being parsed.

This is an example of an internal entity:

<!ENTITY vers '1.0.2'>

And here are some examples of external entities:

<!ENTITY header SYSTEM "header-&vers;.xml"> (parsed)
<!ENTITY logo SYSTEM "logo.png" PNG> (unparsed)

-- (Two hyphens.) Terminates the list of options. This is only
needed if a filename starts with a hyphen. For example:

xmlwf -- -myfile.xml

will run xmlwf on the file -myfile.xml.

Older versions of xmlwf do not support reading from standard input.

OUTPUT

xmlwf outputs nothing for files which are problem-free. If any input
file is not well-formed, or if the output for any input file cannot
be opened, xmlwf prints a single line describing the problem to
standard output.

If the -k option is not provided, xmlwf halts upon encountering a
well-formedness or output-file error. If -k is provided, xmlwf
continues processing the remaining input files, describing problems
found with any of them.

EXIT STATUS

For options -v|--version or -h|--help, xmlwf always exits with status
code 0. For other cases, the following exit status codes are
returned:

0 The input files are well-formed and the output (if requested)
was written successfully.

1 An internal error occurred.

2 One or more input files were not well-formed or could not be
parsed.

3 If using the -d option, an error occurred opening an output
file.

4 There was a command-line argument error in how xmlwf was
invoked.

BUGS

The errors should go to standard error, not standard output.

There should be a way to get -d to send its output to standard output
rather than forcing the user to send it to a file.

I have no idea why anyone would want to use the -d, -c, and -m
options. If someone could explain it to me, I'd like to add this
information to this manpage.

AUTHOR

This manual page was originally written by Scott Bronson
<bronson@rinspin.com> in December 2001 for the Debian GNU/Linux
system (but may be used by others). Permission is granted to copy,
distribute and/or modify this document under the terms of the GNU
Free Documentation License, Version 1.1.

March 27, 2025 XMLWF(1)