There are two things to note in this set of operations.
When you multiply, you must use an escape character before the
multiplication operator for the command to parse correctly, which is why
you see \ (the escape character) before the * (the multiplication
character).
When you divide, only the whole number result will be returned, so, for
example, expr 11 / 3 returns 3 . To get the remainder, use the
following, which returns 2 :
expr 11 / 3There are a number of string-related operations available. Each involves
adding a second word to the command before the string to be evaluated.
To find the length of a string, use the following:
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expr length string
If the string includes spaces, you must again use the escape character, like
this:
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expr length linux\ is\ cool
13
There are many more things you can do with expr. Read the man page for
more information.
The case Statement
You use the case statement to execute statements depending on a discrete
value or a range of values matching the specified variable. In most cases, you
can use a case statement instead of an if statement if you have a large
number of conditions.
The format of a case statement for pdksh and bash is as follows:
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case str in
str1 | str2)
Statements;;
str3|str4)
Statements;;
*)
Statements;;