This chapter will show how variables are used in a Linux system and in scripts.
The topics covered in this chapter are:
A variable is simply a placeholder for some value. The value can change; however, the variable name will always be the same. Here is a simple example:
a=1
This assigns the value 1
to variable a
. Here's another one:
b=2
To display what a variable contains use the echo
statement:
echo Variable a is: $a
If at anytime, you aren't seeing the results you expect first check for the $
.
Here's an example using the command line:
$ a=1 $ echo a a $ echo $a 1 $ b="Jim" $ echo b b $ echo $b Jim
All variables in a Bash script are considered to be strings. This is different than in a programming language such as C, where everything is strongly typed. In the preceding example, a
and b
are strings even though they appear to be integers.
Here's a short script to get us started:
#!/bin/sh # # 6/13/2017 # echo "script1" # Variables a="1" b=2 c="Jim" d="Lewis" e="Jim Lewis" pi=3.141592 # Statements echo $a echo $b echo $c echo $d echo $e echo $pi echo "End of script1"
And here is the output when run on my system:
Since all of the variables are strings I could have also done this:
a="1" b="2"
It is important to quote strings when they contain blank spaces such as variables d
and e
here.