Separates Values in environment variablesĪppend to file, ignore error if not there List of Special Characters and what they mean Character I just wanted you to realize this stuff can be complicated.Īnd if aren't sure if something is a special character or not, it's a good idea to use quotes just in case. There is a lot of detail on this chart, and it's far from complete.įrankly, skip over this for now. I have also included several combinations of characters just to make this table Here is a chart of the meta-characters the Bourne and C shell know There are some tricky bits, but I will mention them later when I cover the different shells. In other words, it doesn't matter which shell you use - because they all understand the three methods of quoting/escaping meta-characters - more or less. That is, what I describe here holds for all of the major varieties of shells, including the dreaded C shell. I wrote this tutorial in a shell-agnostic manner. To quote that character, so that it is passed to the program without If you need a regular expression, you must know if any of theĬharacters of the expression are meta-characters, and must know

It could be the beginning of a variable name, or it could be When you quote a character, you ask the shell to leave it alone - and pass it on unchanged to the utility. In other works, you put quotes around the meta-characters to inticate to the shell that they are not special - as far as the shell is concerned. I want the utility to treat them special, not you!' The mechanism to do this is called quoting. Or to put it another way, you want to say 'Hey Shell. Some characters are special to the Unix shell, and some are special to a utility like sed or grep.īefore you study regular expressions, it is important that you understand how to use the shell to send regular expressions to a program. The actual meaning depends on the program that sees this meta-character.

This is part of my Unix tutorials series.įirst thing you have to understand is that certain characters, called meta-characters, have special meanings.

Including identical quotes within quotes.

The verbose and echo variables in the C shell.

Using quotes to include spaces and characters in filenames.

Quoting a single character with the backslash.

Written by Bruce Barnett Table of Contents

The cat returns quotes