Accessing the UNIX shell from the z/OS TSO session is really simple and it was the only thing I really wanted to see. I will only highlight some point of interest from the UNIX perspective here, like the shell environment, structure, commands and compilers. We will build a simple C program in the end.
So once we login via TSO
In the menu we will select option 6 [Command] <ENTER>
And enter the TSO command OMVS
– Following is taken from the https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zconcepts/zconc_whatiszunix.htm
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.
You use the OMVS command to invoke the z/OS UNIX shell.
The shell is a command processor that you use to:
- Invoke shell commands or utilities that request services from the system.
- Write shell scripts using the shell programming language.
- Run shell scripts and C-language programs interactively (in the foreground), in the background, or in batch.
Shell commands often have options (also known as flags ) that you can specify, and they usually take an argument, such as the name of a file or directory. The format for specifying the command begins with the command name, then the option or options, and finally the argument, if any.
For example, in Figure 1 the following command is shown:
ls -al /u/rogers
where ls is the command name, and -al are the options.
ROGERS @ SC43:/>ls -al /u/rogers total 408 drwx------ 3 ADMIN SYS1 8192 Aug 1 2005 . dr-xr-xr-x 93 AAAAAAA TTY 0 Feb 13 11:14 .. -rwxr-xr-x 1 ADMIN SYS1 979 Feb 29 1996 .profile -rw------- 1 ADMIN SYS1 29 Mar 1 1996 .sh_history -rw-r--r-- 1 AAAAAAA SYS1 84543 Apr 28 2007 Sc.pdf drwxr-xr-x 2 AAAAAAA SYS1 8192 Jun 25 2001 data -rw-r--r-- 1 AAAAAAA SYS1 47848 Jun 26 2004 inventory.export -rwx------ 1 AAAAAAA SYS1 16 Aug 1 2005 myfile -rw-r--r-- 1 AAAAAAA SYS1 43387 Jun 22 2007 print.export
This command lists the files and directories of the user. If the pathname is a file, ls displays information on the file according to the requested options. If it is a directory, ls displays information on the files and subdirectories therein. You can get information on a directory itself by using the -d option.
If you do not specify any options, ls displays only the file names. When ls sends output to a pipe or file, it writes one name per line; when it sends output to the terminal, it uses the -C (multi-column) format.
Terminology note: z/OS users tend to use the terms data set and file synonymously, but not when it comes to z/OS UNIX System Services. With the UNIX support in z/OS, the file system is a data set that contains directories and files. So file has a very specific definition. z/OS UNIX files are different from other z/OS data sets because they are byte-oriented rather than record-oriented.
So we will end up with the following screen
One important thing to understand here is the prompt at the bottom of the x3270 terminal
===> this is were all the commands go (it is slightly weird to get used to )
We can run stuff like “id , whoami, env … ”
Check the process tree via ps
the filesystem is not complex and is quite simple realy, most system binaries reside in /bin, /usr/sbin and /usr/lpp as we can see from the above screenshot
Even Java is there (in this example it is an aged version of z/OS)
sshd and all the related programs are available (again aged in this version)
And of course some C compilers
And finally a small test to compile a simplest of C programs … unfortunately I could not figure out how to define the x3270 terminal for the vi editor so I have used ed instead.
Ed is a single line editor which you can use in emergencies like this :)