7.5. Testing Your Knowledge of Tests

The systemwide xinitrc file can be used to launch the X server. This file contains quite a number of if/then tests. The following is excerpted from an "ancient" version of xinitrc (Red Hat 7.1, or thereabouts).

if [ -f $HOME/.Xclients ]; then exec $HOME/.Xclients elif [ -f /etc/X11/xinit/Xclients ]; then exec /etc/X11/xinit/Xclients else # failsafe settings. Although we should never get here # (we provide fallbacks in Xclients as well) it can't hurt. xclock -geometry 100x100-5+5 & xterm -geometry 80x50-50+150 & if [ -f /usr/bin/netscape -a -f /usr/share/doc/HTML/index.html ]; then netscape /usr/share/doc/HTML/index.html & fi fi

Explain the test constructs in the above snippet, then examine an updated version of the file, /etc/X11/xinit/xinitrc, and analyze the if/then test constructs there. You may need to refer ahead to the discussions of grep, sed, and regular expressions.