Features required for the POSIX shell script include:
- Running commands convenient syntax for running commands, including other programs, specifying arguments, environment variables, working directories, permissions masking, and other properties.
- Variables that can be set to any string value, including manipulating process environment variables, and that can be expanded on the command line.
- Arithmetic expansion for performing integer-based arithmetic on variables and numbers.
- Control structures for executing code depending on the outcome of another command (if), including a specially-designed test or [ command, and repeating code until a condition is true (while).
- Aliases as a way to abbreviate long command lines ...
