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16. Unix Specific Services

The modules described in this chapter provide interfaces to features that are unique to the Unix operating system, or in some cases to some or many variants of it. Here's an overview:

`posix` |  | The most common POSIX system calls (normally used via module `os`).
`pwd` |  | The password database (`getpwnam()` and friends).
`spwd` |  | The shadow password database (`getspnam()` and friends).
`grp` |  | The group database (`getgrnam()` and friends).
`crypt` |  | The `crypt()` function used to check Unix passwords.
`dl` |  | Call C functions in shared objects.
`termios` |  | POSIX style tty control.
`tty` |  | Utility functions that perform common terminal control operations.
`pty` |  | Pseudo-Terminal Handling for SGI and Linux.
`fcntl` |  | The `fcntl()` and `ioctl()` system calls.
`pipes` |  | A Python interface to Unix shell pipelines.
`posixfile` |  | A file-like object with support for locking.
`resource` |  | An interface to provide resource usage information on the current process.
`nis` |  | Interface to Sun's NIS (Yellow Pages) library.
`syslog` |  | An interface to the Unix syslog library routines.
`commands` |  | Utility functions for running external commands.