Learning Linux Shell Scripting - Second Edition

Using a declare command for arithmetic

Whenever we declare any variable, by default, this variable stores the string type of data. We cannot do arithmetic operations on them. We can declare a variable as an integer by using the declare command. Such variables are declared as integers; if we try to assign a string to them, then bash assigns 0 to these variables.

Bash will report an error if we try to assign fractional values (floating points) to integer variables.

We can create an integer variable called value, shown as follows:

    $ declare -i value
  

We tell the shell that the variable value is of type integer. Otherwise, the shell treats all variables as character strings:

• If we try to assign the name string to the integer variable value ...