How to execute PlPgSql from Command line

Hello guys,
please could someone answer my question? how to run a plpgsql script from
the command line? is possible to run like that? i hava a set of scripts to
run. for example insertion for one table, updation for another table.
otherwise is there any option to save those scripts in a file and through
some command can i execute from the command line? if so, what should be the
extension of file & what is the command to run that file. please suggest me
some solution.