Is there an easy way to read arbitrary lines from a file? For example "read line number 12" or "read backwards from last line to first line" or "read lines 1,3,5…".
Filesystem Access – How to Read Arbitrary Lines from a File
filesystem-access
Related Solutions
The short answer is yes. The longer answer is that we'd need more information. You can easily read a file one line at a time. The e-TeX extension \readline is especially helpful for reading files.
How are these lines numbered? How many do you want to read at once? Are the lines sorted by these "specific numbers"? Is your list of numbers sorted? What else can you tell us about these lines?
If you want only the file myfile2.txt to be readable, the solution may be as follows:
\documentclass{article}
\usepackage{xstring}
\usepackage{filecontents}
% WORKS FINE !!!
\begin{filecontents*}{myfile1.txt}
mean: 0.26068087303584447 lablab
\end{filecontents*}
% if in my file there are special characters (e.g #) then I get errors :( !!!
\begin{filecontents*}{myfile2.txt}
# mean: 0.26068087303584447 lablab
\end{filecontents*}
\newread\myread
\newcommand{\readmean}[1]{
\openin\myread=#1
\read\myread to \mystr
\StrBetween{\mystr}{mean: }{ lablab}[\mymean]
\closein\myread
}
\begin{document}
\readmean{myfile1.txt}
mean1 : \mymean
{\catcode`\#=11
\readmean{myfile2.txt}
mean2 : \mymean
}
\end{document}
Best Answer
No, you can't read arbitrary lines, but you can't do that in most other programming languages either. You have to read line after line from the beginning. Apart from the
\readprimitive, there is also the\readlineprimitive which reads a line verbatim. You can use that to save all lines in macros and use these afterward: