How to get only “Chapter 1. The title of the chapter” in the left of header

Question

I am trying to use fancyhdr, but I can't get it to not show the section and to keep the normal case for title and 'Chapter'.

How can I have my heading to be "Chapter 1. The title of the chapter" (left aligned on all pages)

Answer 1

\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt} % optional
\fancyhead[L]{\nouppercase{\leftmark}}
\fancyhead[R]{\thepage}

Answer 2

The titlesec package offers a very good alternative to the fancyhdr package for designing page styles; here's a little example doing what you need:

\documentclass{book}
\usepackage[pagestyles]{titlesec}
\usepackage{lipsum}% to generate filler text

\newpagestyle{mystyle}{%
  \headrule\sethead{\chaptername\ \thechapter. \chaptertitle}{}{}
  \setfoot{}{\thepage}{}}
\pagestyle{mystyle}

\begin{document}

\chapter{Test chapter}
\section{Test section}
\lipsum[1-40]

\end{document}

delete \headrule if you don't need the rule below the headline.