how to use expr

Linux and Unix-Like Red Hat
1

i am new to shell programming, currently using redhat linux of version
2.4.20-8.
i have problem in executing expr command in the following shell script

$ x=5
$ x='expr $x + 1'
$ echo $x

the output is displaying always
expr $x + 1

Pls guide me for the above query

2

You need to use back tics not single quotes

x=`expr $x + 1`

3

I tried to use expr for multiplication, but got an error. I used '*' symbol. Can you tell me what's the problem, or if there is another way? Thanks

4

escape the * it is a shell metacharacter

a=$( expr 13 \* 3)
# or
a=`expr 13 \* 3`