Writing TeX file name at the top of the processed document for article class

Question

Consider the following MWE.

\documentclass{article}
\usepackage{textpos}
\newcommand{\insertname}{%
  \begin{textblock}{2}(5,-0.5)
    \bfseries{\jobname.tex}
  \end{textblock}
}
\begin{document}
\insertname
Some text.
\end{document}

This places the name of the LaTeX file at the top of the output PDF. However, I'd like this handled automatically, using xpatch, if possible. Then I won't need to manually insert the macro into the body, but will have this handled in the preamble. I've tried using \xpretocmd with \maketitle and \titlepage as arguments in turn, but it does not work. Any suggestions how I can do this?

\documentclass{article}
\usepackage{textpos}
\usepackage{xpatch}
\newcommand{\insertname}{%
  \begin{textblock}{2}(5,-0.5)
    \bfseries{\jobname.tex}
  \end{textblock}
}
\xpretocmd{\maketitle}{\insertname}{}{}
%\xpretocmd{\titlepage}{\insertname}{}{}
\begin{document}
%\insertname
Some text.
\end{document}

The answer by tohecz looks good, but doesn't work with a simple letter example.

\documentclass[11pt]{letter}
\address{Sender address}
\signature{Some person}

\usepackage{fancyhdr}
\fancyhf{}
\fancyhead[RO,LE]{\jobname\quad\the\day.~\the\month.~\the\year}
\pagestyle{fancy}

\begin{document}
\begin{letter}{Recipient address}

\opening{Dear Sir/Madam,}

Some stuff

\closing{Thanking you}
\end{letter} 
\end{document}

Answer 1

Something like this

\documentclass[a4paper]{memoir}
% picture loaded to be able to use 'units in \put
\usepackage{eso-pic,picture}
\AddToShipoutPictureBG*{
  % change reference point to page upper left
  \AtPageUpperLeft{
    \put(1cm,-1cm){\textbf{\jobname}}
  }
}
% this is just to have some contents
\usepackage{lipsum}
\begin{document}
\lipsum
\end{document}

\AddToShipoutPictureBG* just added to the next shipped out page. Remove the * and it is added to all pages.

---

Centered version

\documentclass[a4paper]{memoir}
% picture loaded to be able to use 'units in \put
\usepackage{eso-pic,picture,calc}
\AddToShipoutPictureBG*{
  % change reference point to page upper left
  \AtPageUpperLeft{
    \put(\oddsidemargin+1in+0.5\textwidth,-1cm){%
      \makebox[0pt][c]{\textbf{\jobname}}}
  }
}
% this is just to have some contents
\usepackage{lipsum}
\begin{document}
\lipsum
\end{document}

Answer 2

You need to use \maketitle if you want that \insertname is executed.

However the simplistic solution of doing \AtBeginDocument{\insertname} will not work if \maketitle is used in the document, because \maketitle does \newpage.

A more complex workaround is needed if you plan not using \maketitle in your document. If you plan to use it, then \@maketitle is the macro to be patched:

\makeatletter
\xpatchcmd{\@maketitle}{\newpage}{\newpage\insertname}{}{\ddt}
\makeatother

so \insertname is executed after the \newpage.

If you want it independent of the presence of \maketitle, the only reliable way seems to be with a suitable page style.

\documentclass{article}
\usepackage{xpatch}
\makeatletter
\def\ps@faheem{%
  \let\@mkboth\@gobbletwo
  \def\@oddhead{\hfil\textbf{\jobname.tex}}%
  \def\@oddfoot{\reset@font\hfil\thepage\hfil}%
  \let\@evenhead\@empty\let\@evenfoot\@oddfoot
}
\AtBeginDocument{\thispagestyle{faheem}}
\xpatchcmd{\maketitle}{plain}{faheem}{}{}
\makeatother

\begin{document}
\title{A}\author{B}
\maketitle
Some text.
\end{document}

If you comment \maketitle you'll get the same header.

---

For completeness, here's a different strategy with atbegshi:

\documentclass{article}
\usepackage{atbegshi,picture}
\newcommand{\insertname}{%
  \put(\dimexpr\oddsidemargin+1in+\textwidth,-1cm){%
    \makebox[0pt][r]{\textbf{\jobname.tex}}%
  }%
  \gdef\insertname{}%
}
\AtBeginShipout{%
  \AtBeginShipoutUpperLeft{\insertname}%
}

\begin{document}
\title{A}\author{B}
\maketitle
\end{document}

Modify the placement parameters; with this setting, the filename is placed with its right edge flush with the right margin, the baseline at 1cm from the top of the paper.

Answer 3

Do I miss something or you can simply use the standard headers as I often do?

\usepackage{fancyhdr}
\fancyhf{}
\fancyhead[RO,LE]{\jobname\quad\the\day.~\the\month.~\the\year}
\pagestyle{fancy}

This inserts the \jobname and the date of compilation into the header of every page. If you already have something in your header and you want to put this a bit higher, you can use the following construct:

\usepackage{fancyhdr}
\usepackage{mathtools}
\newcommand\jobinhead{\jobname\quad\the\day.\the\month.\the\year}
\fancyhead[RO]{%
  blabla%
  \smash{\raisebox{\baselineskip}{\llap{\jobinhead}}}%
}
\fancyhead[LE]{%
  \leavevmode
  \smash{\raisebox{\baselineskip}{\rlap{\jobinhead}}}%
  blabla%
}
\pagestyle{fancy}

If you don't want to load mathtools, you can simulate \llap{abc} and \rlap{abc} by \hbox to 0pt{\hss abc} and \hbox to 0pt{abc\hss}