You can develop your own utility programs using any language, although ILE/C, ILE/C++, and Java have the best runtime support. When creating ILE/C or ILE/C++ programs, you should use Integrated File System I/O when creating all of the modules in your utility program.
A utility reads input from standard input or descriptor 0, writes output to standard output or descriptor 1, and writes errors to standard error or descriptor 2.
If your utility program uses the ILE/C or ILE/C++ standard files for I/O, you can run your utility from either the qsh command line or the QCMD command line. If your utility reads and writes directly from descriptors 0, 1, and 2, you can only run your utility from the Qshell command line.