How can I use arrays in unix shell?
Well, bash does have arrays, see man bash. The generic posix shell does not.
The shell is not precisely a macro processor, however, and so any metaprogramming must be processed by an eval or, in bash, with the ${!variable} syntax. That is, in a macro processor like nroff you can easily fake up arrays by making variables called a1, a2, a3, a4, etc.
You can do that in the posix shell but requires a lot of eval's or the equivalent like $(($a)).
$ i=1 j=2; eval a$i=12 a$j=34$ for i in 1 2; do echo $((a$i)); done1234$ And for a bash-specific example...
$ a=(56 78)$ echo ${a[0]}56$ echo ${a[1]}78$