related to Substring of filename in LaTeX and extract number from \jobname as counter .
I am naming my filenames as 01-text1.tex, 02-something.tex, 03-blah.tex and so on. I would like to set my section counter according to the first two letters (digits). something like
\setcounter{section}{\StrLeft{\jobname}{2}}
\addtocounter{section}{-1}
this was less than successful, probably catcodes :-(. can someone please recommend the magical invokation that works?
you need an expandable command if you are going to inline it into \setcounter xstring commands are mostly not expandable.
\def\getprefix#1-#2\relax{#1}
\setcounter{section}{\expandafter\getprefix\jobname\relax}
should work.
While it is true that letters in \jobname have strange catcodes that isn't actually an issue here as the digits are the usual catcode 12.
The usual problem: this is not expandable.
Workaround: compute the string beforehand:
\documentclass{article}
\usepackage{xstring}
\begin{document}
\StrLeft{\jobname}{2}[\temp]
\setcounter{section}{\temp}
\addtocounter{section}{-1}
\section{Title}
text
\end{document}
Simpler solution:
\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\setcounter{section}{ \str_range:Nnn \c_sys_jobname_str { 1 } { 2 } }
\addtocounter{section}{-1}
\ExplSyntaxOff
\begin{document}
\section{Title}
text
\end{document}
Of course there is a lower level solution, but much less fun:
\documentclass{article}
\begingroup\def\welch#1#2#3\welch{#1#2}
\setcounter{section}{\expandafter\welch\jobname..\welch}
\addtocounter{section}{-1}
\endgroup
\begin{document}
\section{Title}
text
\end{document}
