Leveraging the ZOSLIB library

What is ZOSLIB?

ZOSLIB is a z/OS C/C++ library. It is an extended implementation of the z/OS LE C Runtime Library.

ZOSLIB implements the following:

• A subset of POSIX APIs that are not available in the LE C Runtime Library
• Overrides for C open, pipe, and more for improved functionality with z/OS auto-conversion facilities.
• EBCDIC <-> ASCII conversion C APIs
• APIs for improved diagnostic reporting
• and more!

You can find more details at the ZOSLIB github page.

The corresponding zopen project lives here.

How can ZOSLIB help my project?

As we continue to port projects to z/OS, we have come across many common issues. Rather than repeating the same patterns and duplicating the solutions on a per project basis, we decided to take a different approach. We decided to solve the issues by linking to an intermediary library, ZOSLIB.

ZOSLIB is an actively developed library that's currently being used by 20+ zopen community projects, including curl, git, bash and more.

ZOSLIB aims to automatically resolve the following types of issues:

• Tagging file descriptors which are not tagged appropriately via C open, mkstemp or pipe.
• Missing POSIX/glibc function or types. (e.g. posix_spawn)
• Missing header files. (e.g. sys/mount.h)

As an example, the C open function has been overridden to automatically tag new files as ASCII, and similarly for C pipe and mkstemp. When zoslib is added to your project, in the case of C open function, all references to open are mapped to a new zoslib __open_ascii function (defined here), which implements this auto-tagging logic.

How do I use zoslib?

Very easily!

Through the zopen framework, all you need to do is to add zoslib as a dependency as follows:

export ZOPEN_DEPS="curl gzip tar make zoslib"

Here's a real example where the curl port added zoslib as a dependency.

How does this work?

This works because ZOSLIB exposes a set of environment variable flags via it's buildenv. These environment variable will automatically be added to your project when it is included as a dependency. They instruct the compiler to pick up the header files and link to the appropriate zoslib static archive.

How do I contribute?

We are happy to accept community code changes! Open a pull request at https://github.com/ibmruntimes/zoslib/pulls