Creating a shell variable

The shell also lets you create variables. A shell variable name can consist of uppercase or lowercase letters, plus digits and the underscore character _. The name can have any length, but the first character cannot be a digit. Uppercase letters are distinguished from lowercase ones, so NAME, name, and Name are all different names.

To create a shell variable, just enter:

set name='string'

as a command to the shell. For example:

set home='/usr/adams'

sets up a variable with the name home and the value /usr/adams.

After you set a variable, you refer to it by prefixing its name with a dollar sign ($). Any command can use the value of a variable by referring to it this way. For example, if home is set to /usr/adams:

cd $home

is equivalent to:

cd /usr/adams

Similarly:

cp $home/* /newdir

is equivalent to:

cp /usr/adams/* /newdir

To change the value of an existing variable, you use a command with the same form as the existing variable. For example:

set home='/usr/benjk'

changes the value of home from /usr/adams to /usr/benjk.

If the value on the right-hand side of the = sign does not contain spaces, tab characters, or other special characters, you can leave out the single quotation marks. For example, you can enter:

home=/usr/benjk