You have downloaded a file to your "Download" area (which happens
frequently). You want to open the file. <br>
<pre>
$ open "$(ls -1tr | tail -1)" 
</pre>
Explanation: <i>ls -1tr</i> lists the files in the directory with the lastest
the oldest file first and the latest line last (time ordered reverse sort);
the option <i>-1</i> (one, not ell) forces each file name to be listed on a separate line.
<i> tail -1 </i> extracts the last line. These two actions are done in a
subshell $(...)$. 
The output of the subshell serve as
input to the <i>open</i> command. The output is enclosed in " " to accommodate
file names with blanks.
<p>
If you start using this command sequence then write a shell executable tool.
Put in your PATH

<pre>
#!/bin/zsh
#
# usage:  
#   latestfile  .. displays the name of the latest file in current directory
#   latest -op  .. opens file with application specified by op
#   	-o      .. use "open"
#       -v      .. use "vi"
#       -any    .. use "any"


a="$(ls -1tr | tail -1)"   #capture last name 

if [ $# -gt 1 ]; then            #check for bad or incorrect usage
  echo "too many paramters: quit"; exit -1
fi

if [ $# = 0 ]; then
	echo $a; exit
fi

if [ $1 = "-o" ]; then
	open "$a"; exit
   elif [ $1 = "-v" ]; then
	vi "$a"
   else
	${1#-} "$a"
fi
</pre>