How to make a stand alone eps file by using Feynmp

Feynmp(Feynmf) is found on http://www.ctan.org/tex-archive/macros/latex/contrib/feynmf/

# emacs test.tex &

\documentclass{article}
\usepackage{feynmp}
\pagestyle{empty}
\begin{document}
\unitlength = 1mm
\begin{fmffile}{example1}
\begin{fmfchar*}(40,25)
  \fmfleft{em,ep} \fmflabel{$e^+$}{ep} \fmflabel{$e^-$}{em}
  \fmf{fermion}{em,Zee,ep}
  \fmf{photon,label=$\gamma,,Z$}{Zee,Zff}
  \fmf{fermion}{fb,Zff,f}
  \fmfright{fb,f} \fmflabel{$\bar f'$}{fb} \fmflabel{$f$}{f}
  \fmfdot{Zee,Zff}
\end{fmfchar*}
\end{fmffile}
\end{document}

# latex test.tex
# mpost example1.mp
# latex test.tex

# dvips -E test.dvi -o test.eps 

OR

# bash_script.sh

#!/bin/sh

for f in *.tex; do
    latex $f;
done
for f in *.mp;  do
    mpost $f;
done
for f in *.tex; do
    latex $f;
done

for f in *.dvi; do
    dvips -E  $f -o $f.eps ;
done

The test.tex file is the exact same code that can be found in the simple examples of feynmp or feynmf except \pagestyle{empty} and the output file name such as example1.  Without the empty style,  dvips command cannot produce an eps file with the correct bounding box owing to the page number.

one more example is

\documentclass{article}
\usepackage{feynmp}
\pagestyle{empty}
\begin{document}
\unitlength = 1.5mm

\begin{fmffile}{em_mpfile}
\fmfcmd{%
  style_def proton expr p =
  save mp, sp; pair mp; path sp;
  mp = point length(p)/2 of p;
  sp = p shifted -mp scaled 1.1 shifted mp;
  cdraw sp shifted (thick*( 2.2,0));
  cdraw sp shifted (thick*(-2.2,0));
  draw_fermion p
  enddef;
}
\begin{fmfchar*}(40,25)
  \fmfleft{ei,ef}  \fmflabel{$e^- (k_1)$}{ei} \fmflabel{$e^-(k_2)$}{ef}
  \fmfright{pi,pf} \fmflabel{$N(p_1)$}{pi} \fmflabel{$N(p_2)$}{pf}
  \fmf{photon,label=$\gamma$}{ve,vp}
  \fmf{fermion}{ei,ve,ef}
  \fmflabel{$ie\gamma^\mu$}{ve}
  \fmf{proton}{pi,vp,pf}
  \fmfblob{.1w}{vp} \fmfv{l=$ie\Gamma^\nu$, l.a=0, l.d=.1w}{vp}
\end{fmfchar*}
\end{fmffile}
\end{document}

The modified source is

\documentclass{article}
\usepackage{feynmp}
\pagestyle{empty}
\begin{document}
\unitlength = 1.5mm
\begin{fmffile}{weak_mpfile}
\fmfcmd{%
  style_def proton expr p =
  save mp, sp; pair mp; path sp;
  mp = point length(p)/2 of p;
  sp = p shifted -mp scaled 1.1 shifted mp;
  cdraw sp shifted (thick*( 2.2,0));
  cdraw sp shifted (thick*(-2.2,0));
  draw_fermion p
  enddef;
}

\def\particlelabel#1#2#3{%
\fmfv{label=#1, label.angle=#2, label.distance=0}{#3}}

\begin{fmfgraph*}(42,26)
  \fmfleft{ei,ef}
  \fmf{fermion}{ei,ve,ef}
  \fmf{dashes, label=$Z^0$}{ve,vp}
  \fmf{proton}{pi,vp,pf}
  \fmfright{pi,pf}
%  \fmflabel{$e^-(k_2,s_2)$}{ef}
%  \fmfv{l=$e^-(k_2,s_2)$}{ef}
%  \fmfv{label=$P(p_1,S_1)$}{pi}
%  \fmfv{label=$P(p_2,S_2)$}{pf}
  \fmfv{decor.shape=circle, decor.filled=50, decor.size=.1w}{vp}
  \particlelabel{$e^-(k_1,,s_1)$}{-90}{ei}
  \particlelabel{$e^-(k_2,,s_2)$}{ 90}{ef}
  \particlelabel{$P(p_1,,S_1)$}{-90}{pi}
  \particlelabel{$P(p_2,,S_2)$}{ 90}{pf}
%  \fmflabel{$- i \frac{g_z}{2} \tilde \gamma^\mu$}{ve}
\end{fmfgraph*}
\end{fmffile}
\end{document}