Available shells

The shell that you'll likely use for scripting under QNX OS is ksh, a public-domain implementation of the Korn shell. The sh command is usually a symbolic link to ksh.

For more information about this shell, see:

• the Using the Command Line chapter in this guide
• the entry for ksh in the Utilities Reference
• Rosenblatt, Bill, and Arnold Robbins. 2002. Learning the Korn Shell, 2nd Edition. Sebastopol, CA: O'Reilly & Associates. ISBN 0-596-00195-9

QNX OS also supplies or uses some other scripting environments:

• An OS buildfile has a script file section tagged by +script. The mkifs utility parses this script, but it's executed by procnto at boot time. It provides a very simple scripting environment, with the ability to run a series of commands, and a small amount of synchronization.
• The embedded shell, esh, provides a scripting environment for running simple scripts in an embedded environment where the overhead of the full ksh might be too much. It supports the execution of utilities, simple redirection, filename expansion, aliases, and environment manipulation.
• The fat embedded shell, fesh, provides the same limited environment as esh, but supplies additional builtin commands for commonly used utilities to reduce the overhead of including them in an embedded system. The fesh shell includes builtins for cp, df, ls, mkdir, rm, and rmdir, although in most cases, the builtin provides only the core functionality of the utility and isn't a complete replacement for it.
• The micro-embedded shell, uesh, provides a subset of esh's functionality, and is suitable for situations with very limited memory.
• python is a powerful object-oriented language that you can use for processing files, manipulating strings, parsing HTML, and much more.
• sed is a stream editor, which makes it most useful for performing repeated changes to a file or set of files. It's often used for scripts, or as a utility within other scripts.
• gawk (GNU awk) is a programming language for pattern matching and working with the contents of files. You can also use it for scripting or call it from within scripts.

In general, a shell script is most useful and powerful when working with the execution of programs or modifying files in the context of the filesystem, whereas sed and gawk are primarily for working with the contents of files. For more information, see:

• the entries for gawk and sed in the Utilities Reference
• Robbins, Arnold, and Dale Dougherty. 1997. sed & awk, 2nd Edition. Sebastopol, CA: O'Reilly & Associates. ISBN 1-56592-225-5