Ubuntu Manpage: xmlwf - Determines if an XML document is well-formed

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:

       • 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.

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

       • 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.

       • All elements nest properly.

       • 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.

                                        February 29, 2024                                XMLWF(1)