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x2gooptionsstring - Man Page

X2Go Agent Options String Manipulator and Extractor


x2gooptionsstring --help|-h|-?

x2gooptionsstring --man

x2gooptionsstring [<--mode|-m><=| >t[ransform]|-t] [--compact|-c] [--base64|-b] [--debug|-d] [--] options_string [+]|-key[=value] ...

x2gooptionsstring <--mode|-m><=| >e[xtract]|-e [--base64|-b] [--debug|-d] [--] options_string key[=value] ...


x2gooptionsstring is a utility for manipulating and extracting data from options strings as passed to X2Go/NX Agent. For more information about supported options strings, refer to the Options STRINGS section in the X2Go::Server::Agent::NX::Options documentation.

For full support of options string, which are allowed (but not recommended) to include binary data, the special --base64|-b switch is supported. If given, all arguments other than flags must be base64-encoded (making it possible to pass binary data via shells, for instance). The program's output, minus potentially debugging messages, will also be base64-encoded.

Currently, two modes are supported:

Transform (default)

Transformation mode is enabled by default if no mode has been explicitly selected.

Call this program with optional flags, the options string as the first parameter and the transformations to be carried out as additional parameters. At least one additional parameter (i.e., a transformation) must be provided. Transformations are described here briefly, but also in the Transformations section in the X2Go::Server::Agent::NX::Options documentation.

It can either add, remove or replace components.

To add or replace a component, pass key[=value] or +key[=value] as a parameter. The latter syntax is useful if key starts with a dash and would therefore be interpreted as a removal operation. If the options string does not include a key key, it will be appended to the end of the options string. If it already exists, either with no value or a different value, the component will be replaced with the provided value.

To fully remove a component, pass -key. To only remove it if it is set to a specific value, pass -key=value.

Use the --compact option to minimize the original options string, removing duplicated and empty entries.

Assuming no error happened, the resulting options string is written to stdout.


Extraction mode must be explicitly requested using the -e or <--mode|-m><=| >e[xtract] flags.

Call this program with optional flags, the options string as the first parameter and key-value pairs to be extracted as additional parameters. At least one additional parameter (i.e., a key-value pair to extract) must be provided.

A degenerated key-value pair without an explicit value can be used to test for the existence of a key and extract its value at the same time.

A full, proper key-value pair can be used to test for the existence of a key-value pair exactly as provided.

Assuming no error happened, the extracted key-value pairs will be written to stdout. Each pair will be base64-encoded and, if multiple key-value pairs to extract have been provided, delimited via pipe characters (|).

Key-value pairs which haven't been found in the original options string, as well as potentially an empty key-value pair, will be represented as empty fields.

Refer to the Options Parsing section for a description of when and how to terminate options passed to this program.



Print a brief help message and exits.


Prints the manual page and exits.


Enables noisy debug output.


Shorthand for --mode=transform.


Shorthand for --mode=extract.

<--mode|-m><=| >mode string

Selects a specific program mode.

Currently, the following mode strings are supported:

  • transform
  • extract

Mode strings can be abbreviated, as long as the abbreviation is uniquely selecting one mode exactly.


Remove duplicate and empty entries after the initial parsing. The order of arguments is preserved in a first-seen fashion.

This option is only available in transformation mode. It will be silently ignored in extraction mode, as compaction is a pre-requisite and done automatically during extraction.


Enable a special full base64 mode.

Any binary data can be given and output by this program in this mode, even when operating on a shell.

Input parameters must always be provided encoded in base64 form.

Likewise, the program will always output data encoded in a base64 form. Since key-value pairs returned in extraction mode are already base64-encoded and delimited with a character that is not legal in the base64 encoding, this flag does not modify the extraction's mode output (i.e., you will not have to decode the output data twice).

Options Parsing

You can terminate program options parsing via a standard double-dash (--) pseudo-option. It is highly recommended to always do so.

If you pass removal transformation operations or an extraction key-value pair starts with a dash (-), passing the options terminator is mandatory, even if no actual options are used. Otherwise, transformation operations or extraction key-value pairs will be interpreted as options to the program, which will almost certainly lead to an error.

For example, passing -clipboard as a transformation operation without a previous options terminator will be interpreted as the option -c, with the rest of the string modified into -lipboard. Since this program does not accept an option called -l, it will terminate with an error. Even if the program does not terminate with an error due to an unknown option being supplied, a degradation into options is certainly not what the original transformation operation was supposed to represent.



For an options string such as


calling x2gooptionsstring '--' 'nx/nx,clipboard=both,foo:50' '-clipboard' shall return


while calling x2gooptionsstring '--' 'nx/nx,clipboard=both,foo:50' '-clipboard=server' shall return


Calling x2gooptionsstring '--' 'nx/nx,clipboard=both,foo:50' 'bar' shall return


and calling x2gooptionsstring '--' 'nx/nx,clipboard=both,foo:50' '+-bar' 'foo=gulp' '-clipboard=client' shall return


For an options string such as


you can get a compacted version by cheating a bit and providing a transformation which will certainly be a no-operation using x2gooptionsstring '-c' '--' 'nx/nx,clipboard=both,foo=bar,bar=baz,,foo=oof,:50' '-', which shall return



For an options string such as


Calling x2gooptionsstring '-e' '--' 'nx/nx,clipboard=both,foo=bar,-=-,bar=baz,foo=oof,:50' 'foo' shall return


while calling x2gooptionsstring '-e' '--' 'nx/nx,clipboard=both,foo=bar,-=-,bar=baz,foo=oof,:50' 'bar' '' 'clipboard=none' '-' shall return



This manual has been written by Mihai Moldovan <ionic@ionic.de> <mailto:ionic@ionic.de> for the X2Go project (<https://www.x2go.org>).


2024-01-27 Version Unknown - X2Go Server Bug!