2.4) How do I get the current directory into my prompt?
 It depends which shell you are using. It's easy with some
 shells, hard or impossible with others.
 C Shell (csh):
 Put this in your .cshrc - customize the prompt variable the
 way you want.
 alias setprompt 'set prompt="${cwd}% "'
 setprompt # to set the initial prompt
 alias cd 'chdir \!* && setprompt'
 
 If you use pushd and popd, you'll also need
 alias pushd 'pushd \!* && setprompt'
 alias popd 'popd \!* && setprompt'
 Some C shells don't keep a $cwd variable - you can use
 `pwd` instead.
 If you just want the last component of the current directory
 in your prompt ("mail% " instead of "/usr/spool/mail% ")
 you can use
 alias setprompt 'set prompt="$cwd:t% "'
 
 Some older csh's get the meaning of && and || reversed.
 Try doing:
 false && echo bug
 If it prints "bug", you need to switch && and || (and get
 a better version of csh.)
 Bourne Shell (sh):
 If you have a newer version of the Bourne Shell (SVR2 or newer)
 you can use a shell function to make your own command, "xcd" say:
 xcd() { cd $* ; PS1="`pwd` $ "; }
 If you have an older Bourne shell, it's complicated but not
 impossible. Here's one way. Add this to your .profile file:
 LOGIN_SHELL=$$ export LOGIN_SHELL
 CMDFILE=/tmp/cd.$$ export CMDFILE
 # 16 is SIGURG, pick a signal that's not likely to be used
 PROMPTSIG=16 export PROMPTSIG
 trap '. $CMDFILE' $PROMPTSIG
 and then put this executable script (without the indentation!),
 let's call it "xcd", somewhere in your PATH
 : xcd directory - change directory and set prompt
 : by signalling the login shell to read a command file
 cat >${CMDFILE?"not set"} <<EOF
 cd 1ドル
 PS1="\`pwd\`$ "
 EOF
 kill -${PROMPTSIG?"not set"} ${LOGIN_SHELL?"not set"}
 Now change directories with "xcd /some/dir".
 Korn Shell (ksh):
 Put this in your .profile file:
 PS1='$PWD $ '
 
 If you just want the last component of the directory, use
 PS1='${PWD##*/} $ '
 T C shell (tcsh)
 Tcsh is a popular enhanced version of csh with some extra
 builtin variables (and many other features):
 %~ the current directory, using ~ for $HOME
 %/ the full pathname of the current directory
 %c or %. the trailing component of the current directory
 so you can do
 set prompt='%~ '
 BASH (FSF's "Bourne Again SHell")
 
 \w in $PS1 gives the full pathname of the current directory,
 with ~ expansion for $HOME; \W gives the basename of
 the current directory. So, in addition to the above sh and
 ksh solutions, you could use
 PS1='\w $ ' 
 or
 PS1='\W $ '