\documentclass{article}
\usepackage{xstring}
\begin{document}
\StrBehind[2]{/foo/bar}{/}
\StrCount{/foo/bar}{/}
\StrBehind[\StrCount{/foo/bar}{/}]{/foo/bar}{/}
\end{document}
I'm trying to delete /foo/ out of /foo/bar using xstring. The first line in the document above does produce bar and the second line does produce 2, but the third line doesn't work. How do I make it work, or is there a simpler approach to do what I want?
If I understand well what do you want: to expand the last segment separated by slashes from the parameter, i.e. /foo/bar should expand to bar and /foo/bar/next should expand to next. You can define following macro (using only TeX primitives):
\def\afterlastslash#1{\afterlsA#1/\end}
\def\afterlsA#1/#2{\ifx#2\end #1\else \expandafter\afterlsA\expandafter#2\fi}
\afterlastslash{/foo/bar} % expands to bar
\afterlastslash{/foo/bar/next} % expands to next
I think a listofitems approach is simpler.
\documentclass{article}
\usepackage{listofitems}
\setsepchar[,]{/}%
\newcommand\postslash[1]{\readlist\myparse{#1}\myparse[-1]}
\begin{document}
\postslash{/foo/bar}
\postslash{bar}
\postslash{/foo/baz/bar}
\end{document}
I tried doing the same thing with \expandafters, with no sucess. Besides, that much inline code is ugly.
\documentclass{article}
\usepackage{xstring}
\begin{document}
\StrCount{/foo/bar}{/}[\temp]
\StrBehind[\temp]{/foo/bar}{/}
\end{document}
with lualatex
\documentclass{article}
\usepackage{luacode}
\begin{luacode}
function StrBehind(s0)
local s1 = s0:split("/")
tex.print(s1[#s1])
end
\end{luacode}
\newcommand\StrBehind[1]{\directlua{StrBehind("#1")}}
\begin{document}
\StrBehind{/foo/bar}
\StrBehind{/foo/bar/bza/foobar}
\StrBehind{foobar}
\end{document}
Here's an expl3 implementation, named \getbasename. We add /\q_nil/ at the end and test two items at a time (the first can be empty).
Similarly defined is \getdirname that returns the path.
\documentclass{article}
\ExplSyntaxOn
\NewExpandableDocumentCommand{\getbasename}{m}
{
\michel_getbasename:w #1/\q_nil/
}
\cs_new:Npn \michel_getbasename:w #1/#2/
{
\quark_if_nil:nTF { #2 }
{% reached the end, return the previous item
#1
}
{% go on: put back #2/ and test again
\michel_getbasename:w #2/
}
}
\NewExpandableDocumentCommand{\getdirname}{m}
{
\michel_getdirname:w #1/\q_nil/
}
\cs_new:Npn \michel_getdirname:w #1/#2/
{
\quark_if_nil:nF { #2 }
{% return #1/ and go on: put back #2/ and test again
#1/
\michel_getdirname:w #2/
}
}
\ExplSyntaxOff
\begin{document}
\getbasename{/foo/bar}
\getbasename{foo/bar}
\getbasename{/foo//bar}
\getbasename{/foo/bar/next}
X\getbasename{}X
X\getbasename{/}X
X\getbasename{/foo/}X
\getdirname{/foo/bar}
\getdirname{foo/bar}
\getdirname{/foo//bar}
\getdirname{/foo/bar/next}
X\getdirname{}X
\getdirname{/}
\getdirname{/foo/}
\end{document}
The last three examples with \getbasename and the first one with \getdirname return nothing, as witnessed by “XX”.
The function \quark_if_nil:nTF returns true if its (braced) argument contains only \q_nil, false otherwise.
Here is a another approach using underlying TeX capacity with delimited macros. Compared to answer by wipet it is not using conditional tests (which may fail fo various reasons such as braced material, I will give an example), but it also proceeds iteratively and expandably.
\documentclass{article}
\usepackage[T1]{fontenc}% for \texttt{->}
\makeatletter
\catcode`A 3 % create some improbable token as delimiter
% as we are using LaTeX for the demo, perhaps
% we should have used @nil
% switch utility
\long\def\uppera@switch #1A#2#3\relax{#2}
% we incorporate slight overhead to expand in exactly two steps
\long\def\afterlastslash#1{\romannumeral\afterlastslash@i \z@#1/A}
\long\def\afterlastslash@i #1/#2{\uppera@switch #2{#1}A{\afterlastslash@i\z@#2}\relax}
\catcode`A 11
\makeatother
\begin{document}
\newcommand\test[1]{\texttt{\detokenize{\afterlastslash{#1}}} expands to \texttt{\afterlastslash{#1}}}
\test{/oof/bar} % expands to bar
\test{/{oof}/bar} % expands to bar
\test{{braced/path}/bar} % expands to bar
\test{{/path}/bar} % expands to bar
\test{/foo/bar/next} % expands to next
\newcommand\testedef[1]{\texttt{\detokenize{\edef\x{\afterlastslash{#1}}}} gives meaning
\edef\x{\afterlastslash{#1}}\texttt{\meaning\x<after meaning>}}
\testedef{/foo/bar/next}
\testedef{/foo/bar/next/}
Check that two expansions suffice
\expandafter\expandafter\expandafter\def
\expandafter\expandafter\expandafter\x
\expandafter\expandafter\expandafter{\afterlastslash{/foo/bar/next}}
\texttt{\meaning\x<after meaning>}
Show feature of brace removal of output
% a limitation: there is brace removal of last part
\edef\x{\afterlastslash{/foo/bar/{next}}}\texttt{\meaning\x<after meaning>}
Check nesting. We need te expand argument, but our macro was not constructed
to expand it. So let's use \texttt{\string\expanded} and
\texttt{\string\expandafter}.
\begin{verbatim}
\edef\x{\expandafter\afterlastslash\expandafter{%
\expanded{\afterlastslash{/foo/bar/{/foo/bar}}}}}
\end{verbatim}
%
\edef\x{\expandafter\afterlastslash\expandafter{\expanded{\afterlastslash{/foo/bar/{/foo/bar}}}}}\texttt{\meaning\x<after meaning>}
\end{document}
\documentclass{article}
\usepackage[T1]{fontenc}% for \texttt{->}
\makeatletter
\catcode`A 3 % create some improbable token as delimiter
% as we are using LaTeX for the demo, perhaps
% we should have used @nil
% switch utility
\long\def\uppera@switch #1A#2#3\uppera@switch{#2}
% we incorporate slight overhead to expand in exactly two steps
% also we avoid brace removal of last item in this variant
% (thanks to extending it by @nil and also by fetching two
% items at a time)
\long\def\afterlastslash#1{\romannumeral\afterlastslash@i#1@nil/A/}
\long\def\afterlastslash@i #1/#2/{%
% notice that brace removal can happen in intermediate #2 but this
% is not important, as the final "basename" is protected by the added @nil
\uppera@switch #2{\afterlastslash@clean@empty#1}A{\afterlastslash@i#2/}\uppera@switch
}
% @empty token will prevent brace removal in this last step
\long\def\afterlastslash@clean#1@nil{\expandafter\z@#1}
\catcode`A 11
\makeatother
% wipet https://tex.stackexchange.com/a/684771/293669
% \def\afterlastslash#1{\afterlsA#1/\end}
% \def\afterlsA#1/#2{\ifx#2\end #1\else \expandafter\afterlsA\expandafter#2\fi}
\begin{document}
\newcommand\test[1]{\texttt{\detokenize{\afterlastslash{#1}}} expands to \texttt{\afterlastslash{#1}}}
\test{/oof/bar} % expands to bar
\test{/{oof}/bar} % expands to bar
\test{{braced/path}/bar} % expands to bar
\test{{/path}/bar} % expands to bar
\test{/foo/bar/next} % expands to next
\newcommand\testedef[1]{\texttt{\detokenize{\edef\x{\afterlastslash{#1}}}} gives meaning
\edef\x{\afterlastslash{#1}}\texttt{\meaning\x<after meaning>}}
\testedef{/foo/bar/next}
\testedef{/foo/bar/next/}
Check that two expansions suffice
\expandafter\expandafter\expandafter\def
\expandafter\expandafter\expandafter\x
\expandafter\expandafter\expandafter{\afterlastslash{/foo/bar/next}}
\texttt{\meaning\x<after meaning>}
Check no brace removal regarding last item
\edef\x{\afterlastslash{/foo/bar/{last is kept braced}}}\texttt{\meaning\x<after meaning>}
\end{document}
output
