Shell Programming in UNIX / Linux

Intended Audience

• Advanced users
• System and network administrators

Prerequisites

• General training in commercial or free distribution of UNIX or LINUX.
• Programming experience is a plus.

Outline

Module 1. History and flavours of command-line shells. POSIX standard for shells.

• History of shells: Thomson’s sh, rc, Bourne, Korn, California (csh)
• POSIX standard for shells.
• Modern shells: Bourne Again (bash), zsh, tcsh, tclsh

Module 2. VI editor as a fundamental for UNIX shells operation.

• History of editors: ed, em, ex, vi, sed, vim, emacs
• Operation modes of VI editor, using command mode hot keys.
• I Improved for GNU/Linux.

Module 3. Command line editing in shells.

• What is a terminal? Terminal capabilities and behaviour: terminfo command
• vi vs emacs mode, using control keys in different modes.
• Readline in GNU/Linux

Module 4. Basic UNIX and GNU tools for command line operation

• Working with documentation system, navigating and operating file system, searching files and content, hardware information, users information, working with processes.

Module 5. Shell Scripting fundamentals.

• What is script?
• Which shell should interprets script.
• Script format.
• Comments in scripts.
• Portability issues.

Module 6. Variables

• A concept of variables. Environment vs Local variables.
• Variables substitution, conditional substitution.
• Removing variables.
• Shell built-in and special variables.

Module 7. User Input

• Requesting user input: read command.
• Positional parameters (command-line arguments).
• Creating parameters. Shifting parameters.

Module 8. Designing program output

• Basic output: echo vs print
• Formatted output: printf
• Advanced formatting in the terminal: tput

Module 9. Shell Arithmetic

• Math in shell — integer operations.
• Base10, Base2 and other radix.
• Working with arithmetic. Operators.
• Floating-point math using bc tool.

Module 10. Filename generation patterns

• Mass operations on files.
• Available patterns.
• Filename globbing.

Module 11. Branches and Logic Testing

• A concept of Return status
• Logic testing: test command
• Program flow branching constructs: if .. then .. elif .. else and case statements

Module 12. Program loops

• The while and until conditional loops.
• The for iteration loop.
• The select loop.
• Breaking a loop (continue, break, exit).

Module 13. The getopts Command

• Parsing command-line options inside a script: getopts command.
• Special shell variables OPTIND and OPTARG.
• Enhanced option parsing: getopt. getopt vs getopts.

Module 14. Array Variables

• Integer-indexed arrays.
• Substituting and counting all elements.
• Bash-style hash maps.

Module 15. Functions and Function Libraries

• A concept of a shell function.
• Displaying and declaring functions. Variable scope.
• Function execution flow. return command.
• Korn-style function libraries.

Module 16. Managing Input and Output

• A concept of file descriptors. Data flow through a process.
• Managing file descriptors. Special invocation of exec command.
• Passing file contents to a script. Redirecting to a loop within script.
• Using here-documents.

Module 17. Traps and Signals

• A concept of signals. Common and well-known signals.
• Handling a signal: trap command.
• Controlling generation of signals from terminal: stty command.

Module 18. Regular Expressions

• A concept of regular expressions.
• Metacharacters and escaping. Different flavours of regular expressions syntax.
• Applying regular expressions: grep command.
• Perl-compatible regular expressions: pcretest command.

Module 19. Stream Editing with sed

• Mass-processing a text streams: sed command.
• A generic structure of a sed command.
• Printing and deleting lines. Substituting patterns in the text. Reading and writing files.
• Combining sed actions. Sed scripts.
• GNU-specific advanced sed constructs.

Module 20. Introduction to AWK

• Sophisticated text data processing: the awk command.
• Structure of AWK program. Record processing. Pre and Post-input processing.
• Pattern-matching and printing.
• Complex pattern matching. Relational expressions.
• AWK scripts.

Module 21. Variables, Strings, and Arithmetic Operations

• User-defined variables. Reserved variables.
• Accessing the environment and command-line arguments.
• Arithmetic operations. String manipulation.
• Formatting output.

Module 22. AWK Flow Control

• Conditional operator: if
• Loop constructs: for, while
• getline, next and exit.
• One- and multidimensional arrays. Associative arrays.
• Processing arrays using special for loop.
• Invoking external programs: system command.