What is z/OS UNIX?

The z/OS® UNIX® shell and utilities provide an interactive interface to z/OS.

The shell and utilities can be compared to the TSO function in z/OS.

To perform some command requests, the shell calls other programs, known as utilities. The shell can be used to:

Invoke shell scripts and utilities.
Write shell scripts (a named list of shell commands, using the shell programming language).
Run shell scripts and C language programs interactively, in the TSO background or in batch.

Figure 1. Shell and utilities

A user can invoke the z/OS UNIX shell in the following ways:

From a 3270 display or a workstation running a 3270 emulator
From a TCP/IP-attached terminal, using the rlogin and telnet commands
From a TSO session, using the OMVS command.

As an alternative to invoking the shell directly, a user can use ISHELL by entering the command ISHELL from TSO. ISHELL provides an ISPF panel interface to perform many actions for z/OS UNIX operations.

Figure 2 shows an overview of these interactive interfaces, the z/OS UNIX shell and ISHELL. Also, there are some TSO/E commands that support z/OS UNIX, but they are limited to functions such as copying files and creating directories.

Figure 2. z/OS UNIX interactive interfaces

The z/OS UNIX shell is based on the UNIX System V shell and has some of the features from the UNIX Korn shell. The POSIX standard distinguishes between a command, which is a directive to the shell to perform a specific task, and a utility, which is the name of a program callable by name from the shell. To the user, there is no difference between a command and a utility.

The z/OS UNIX shell provides the environment that has the most functions and capabilities. It supports many of the features of a regular programming language.

You can store a sequence of shell commands in a text file that can be executed. This is called a shell script.

The TSO commands used with z/OS UNIX are:

ISHELL: The ISHELL command invokes the ISPF panel interface to z/OS UNIX System Services. ISHELL is a good starting point for users familiar with TSO and ISPF who want to use z/OS UNIX. These users can do much of their work with ISHELL, which provides panels for working with the z/OS UNIX file system, including panels for mounting and unmounting file systems and for doing some z/OS UNIX administration. ISHELL is often good for system programmers, familiar with z/OS, who need to set up UNIX resources for the users.
OMVS: The OMVS command is used to invoke the z/OS UNIX shell. Users whose primary interactive computing environment is a UNIX system should find the z/OS UNIX shell environment familiar.