(1) Variable name must begin with Alphanumeric character or underscore
character (_), followed by one or more Alphanumeric character. For e.g. Valid
shell variable are as follows
(2) Don't put spaces on either side of the equal sign when assigning value to
variable. For e.g. In following variable declaration there will be no error
But there will be problem for any of the following variable declaration:
$ no =10
$ no= 10
$ no = 10
(3) Variables are case-sensitive, just like filename in Linux. For e.g.
Above all are different variable name, so to print value 20 we have to use $
echo $NO and not any of the following
$ echo $no # will
print 10 but not 20
$ echo $No# will print 11 but not 20
$ echo $nO# will print 2 but not 20
(4) You can define NULL variable as follows (NULL variable is variable which
has no value at the time of definition) For e.g.
Try to print it's value by issuing following command
$ echo $vech
Nothing will be shown because variable has no value i.e. NULL variable.
(5) Do not use ?,* etc,
to name your variable names.