LaTeX Forum

\documentclass[tikz]{standalone}
\usetikzlibrary{intersections, through}

\begin{document}
\begin{tikzpicture}
\draw
    node [draw, circle, inner sep=0pt, minimum size=4pt] (c) {}
    (c) -- +(-1,0)
;
\end{tikzpicture}

\begin{tikzpicture}
\draw
    node [draw, circle, inner sep=0pt, minimum size=4pt] (c) {}
    (c) -- +(180:1)
;
\end{tikzpicture}

\begin{tikzpicture}
\pgfmathsetlengthmacro{\radius}{2pt}
\draw 
    (0,0) -- (1cm-\radius,0) 
        arc [start angle=180, end angle=-180, radius=\radius]
;
\end{tikzpicture}

\begin{tikzpicture}
\draw (0,0) -- (1cm-2pt,0) coordinate (line end);
\node [draw, circle through=(line end)] at (1,0) {};
\end{tikzpicture}

\begin{tikzpicture}
\path [name path=line] (0,0) coordinate (O) -- (1,0) coordinate (c);
\draw [name path=circle] (c) circle [radius=2pt];
\draw [name intersections={of=line and circle}] (O) -- (intersection-1);
\end{tikzpicture}
\end{document}

\documentclass[tikz]{standalone}
\begin{document}

\begin{tikzpicture}
\draw (0,0) -- (1,0);
\draw[fill=white] (1,0) circle [radius=2pt];
\end{tikzpicture}

\begin{tikzpicture}
\draw[shorten > = 2pt] (0,0) -- (1,0);
\draw (1,0) circle [radius=2pt];
\end{tikzpicture}

\begin{tikzpicture}
\draw
  (0,0) -- ({1cm-2pt},0)
  (1,0) circle [radius=2pt]
;
\end{tikzpicture}

\begin{tikzpicture}
\path 
  (1,0)
    node [draw,circle,inner sep=0pt,minimum size=4pt](c){}
    edge (0,0)
;
\end{tikzpicture}

\begin{tikzpicture}
\path 
  (0,0) coordinate (O)
  (1,0)
    node [draw,circle,inner sep=0pt,minimum size=4pt](c){}
    edge (O)
;
\end{tikzpicture}
\end{document}

\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}
\draw (0,0) -- (1,0);
\draw (1,0) circle (2pt);
\end{tikzpicture}
\begin{tikzpicture}
\draw (0,0) -- (0.925,0);
\draw (1,0) circle (2pt);
\end{tikzpicture}
\end{document}