Chris F.A. Johnson
Unix shell programming notes

26 March 2013

The colon as a placeholder

When writing a script, I like it always to be a valid script, one that can run without any syntax errors. When I write the outline of a for or while loop, I want it to be an executable piece of code even before I have written the code that will go inside it. The basic loop will not do:

while read line


It will give me an error:

  bash: syntax error near unexpected token `done'

Since such constructs are programmed as macros or functions in my editor, I modified them to create executable code by adding a colon:

while read line
do :


The function macro also puts in comments where I will add at least minimal documentation for the function:

function_name() #@ 
{ :             #@ USAGE: function_name 

It's a small thing, but a useful one.

Modified 01 Jul 2013