Use \csdef on command line to pass in paramaters

Question

Is it possible to use a \csdef{}{} on the command line to pass in parameters to pdflatex?

Background:

If the MWE below is saved as "TeX-SE.tex", I can use the following command line to define the value of \MyCommandViaDef

pdflatex "\def\MyCommandViaDef{123} \input{TeX-SE.tex}"

and things work as desired:

When I need to define a more complicated command that contains file names with dashes, using \def is no longer an option.

I realize I can use

pdflatex "\def\MyCommandViaDef{123} \expandafter\def\csname MyCommand Via Csdef\endcsname{xyz} \input{TeX-SE.tex}"

to obtain the desired results

but using a \csdef{}{} such as would be preferrable.

pdflatex "\def\MyCommandViaDef{123} \csdef{MyCommand Via Csdef}{xyz} \input{TeX-SE.tex}"

Code:

\documentclass{article}
\usepackage{etoolbox}

\begin{document}

Value via def: \MyCommandViaDef

\ifcsdef{MyCommand Via Csdef}{%
    Value via csdef: \csuse{MyCommand Via Csdef}
}{%
    Value via csdef: Not Available
}%

\end{document}

Answer 1

You can use a hook, so you can use \csdef just after etoolbox has been loaded.

pdflatex '\def\MyCommandViaDef{123} \AddToHook{package/etoolbox/after}{\csdef{MyCommand Via Csdef}{xyz}}\input{test}'

This way, the commands will also be available in the preamble.

You may want to do \RequirePackage{etoolbox} before \documentclass.

Answer 2

You can not use \csdef unless you define it first or delay its use (eg with \AtBeginDocument) but you could use built in latex features for example

\ExpandArgs{c}\def{MyCommand Via Csdef}{xyz}

Answer 3

Using

$ pdflatex '\csdef{key1}{value1} \csdef{key2}{value2} \input{<filename>}'

is a hack to work around how TeX processes the command line; a syntax like

$ pdflatex <filename>.tex first-parameter=first-value '{another key}={\textbf{Hello, world!}}'

is much nicer for the end user to use.

To parse arguments written this way, we can use expl3 to read the command line arguments literally:

\ExplSyntaxOn
    %% Initialization code
    \cs_if_exist:NF \g__example_first_run_bool {
        \cs_generate_variant:Nn \prop_set_from_keyval:Nn { NV }

        \str_new:N \g__example_args_str
        \tl_new:N \l__example_args_tl
        \seq_new:N \l__example_args_seq
        \prop_new:N \l__example_args_prop

        \bool_new:N \g__example_first_run_bool
        \bool_gset_true:N \g__example_first_run_bool

        \cctab_const:Nn \c__example_skip_document_cctab {
            \int_set:Nn \tex_endlinechar:D { -1 }
            \int_step_inline:nnn { 0 } { 127 } {
                \char_set_catcode_ignore:n { #1 }
            }
        }
    }

    %% Main code
    \bool_if:NTF \g__example_first_run_bool {
        %% First run: read the arguments from the command line
        \tex_everyeof:D = {
            %% This will run as soon as we reach the end of the file
            \tex_everyeof:D = { } %% Reset to avoid loops

            %% Switch to a new catcode regime
            \cctab_end:
            \cctab_begin:N \c_other_cctab

            %% Read the command line arguments
            \peek_analysis_map_inline:n {
                \exp_args:Ne \token_if_eq_charcode:NNTF {
                    \char_generate:nn { `\^^M } { 11 }
                } #1 {
                    %% If we see ^^M, then we're at the end of the command line
                    %% arguments, so we switch back to normal catcodes and
                    %% input the file again.
                    \cctab_end:
                    \bool_gset_false:N \g__example_first_run_bool
                    \file_input_raw:V \c_sys_jobname_str
                } {
                    %% Otherwise, keep accumulating the arguments.
                    \str_put_right:Nn \g__example_args_str { #1 }
                }
            }
        }
        %% Ignore the rest of the document and proceed to read in the command
        %% line as document content.
        \cctab_begin:N \c__example_skip_document_cctab
    } {
        %% Second run: process the arguments and continue with the document
        \tl_set_rescan:NnV \l__example_args_tl {
            \cctab_select:N \c_document_cctab
        } \g__example_args_str

        \seq_set_split:NVV \l__example_args_seq \c_space_tl \l__example_args_tl
        \seq_map_inline:Nn \l__example_args_seq {
            \prop_put_from_keyval:Nn \l__example_args_prop { #1 }
        }

        \NewDocumentCommand \ShowParameter { m } {
            #1:~ \prop_item:Nn \l__example_args_prop { #1 }
        }
    }
\ExplSyntaxOff

%% Demonstration
\documentclass{article}

\pagestyle{empty}
\setlength{\parindent}{0pt}
\setlength{\parskip}{\baselineskip}

\begin{document}
    \ShowParameter{first-parameter}

    \ShowParameter{another key}
\end{document}

Compiling with above command line then gives the following output: