syntax of for loop in linux shell scripting

linux bash shell for-loop dash-shell

You probably run it with sh, not bash. Try bash test1.sh, or ./test1.sh if it's executable, but not sh test1.sh.

linux bash shell for-loop dash-shell

A standard POSIX shell only accepts the syntax for varname in list

The C-like for-loop syntax for (( expr1; expr2; expr3 )) is a bashism.

You can get similar behavior in the standard POSIX shell using for c in $(seq 1 5)

linux bash shell for-loop dash-shell

What does

ls -l /bin/sh

give on your machine ?

Make sh a symbolic link to bash and then you can do sh ./test1.sh

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