#
# This script can be run with either a Bourne shell or a C shell.
#
# This prepends $HOME/bin to the PATH variable.  Please do not write
# scripts that do tricks like this.  This gives new meaning to the
# word "obfuscated".
#

# This line runs only in Bourne shells.
#
# In Bourne shell, the backslash quotes the following double quote mark, so
# it prints a double quote to /dev/null, executes the line, then prints a
# backslash, a double quote, and another backslash to /dev/null.
#
# In C shell, the backslash is just a normal character inside a string, so the
# following double quote mark ends the string.  The third double quote mark
# reopens it.  This string closes prior to the HOME variable, but that's still
# legal in C shell (assuming HOME and PATH are both defined as they should be),
# so the contents of these variables and the text between them is concatenated
# onto the previous strings.  The next double quote mark starts a string again,
# which includes the single quote and the following backslash before ending at
# the double quote mark in the second echo statement.  Finally, the backslash
# serves to quote the following single quote mark since it is not in a
# string).  Thus, the single quote is treated as a literal character.  The
# resulting line is sent to /dev/null.
#
echo "\"" > /dev/null; export PATH="$HOME/bin:$PATH"; echo '\"\' > /dev/null

# This line runs only in C shells.
#
# In Bourne shell, the backslash causes the following double quote mark to be
# treated as a literal character.  The remaining text up to the third double
# quote mark is part of the string.  Because the ${HOME} construct is legal
# in Bourne shell (though not the normal way of printing a variable), the
# contents of the HOME variable are concatenated, followed by the text after
# it and the contents of the PATH variable.  The next double quote mark starts
# a new string containing a semicolon, the word "echo", and the following
# space.  The double quote that follows the word "echo" ends the string.  The
# backslash quotes the double quote mark that follows it, causing it to be
# treated as a literal character that is concatenated onto the previous string.
# The resulting line of text is then sent to /dev/null.
#
# In C shell, because backslashes inside strings do not quote the character
# that follows them, the first backslash is treated as a literal character, and
# the double quote mark after it ends the string.  Thus, a backslash is sent to
# /dev/null.  Next, the setenv instruction is interpreted as you would expect.
# Finally, as before, the double-quote-backslash-double-quote construct is
# interpreted as a string containing only a backslash, which is sent to /dev/null.
#
echo "\" > /dev/null; setenv PATH "${HOME}/bin:${PATH}"; echo "\" > /dev/null

echo "PATH IS $PATH"