Lesson 1

This course introduces you to the advanced features of the UNIX Bourne shell and teaches you how to apply them effectively. You will also learn new UNIX commands like sed and awk, which are commonly used in shell scripts.
This is the second in a two-part series that teaches UNIX shell programming. This course teaches you to use advanced features of the shell including embedded command execution, command line argument processing, debugging techniques, use of sed to edit files, and use of awk to format command output.
Along the way, you will work on a series of your own shell script projects that will let you put your new skills to work in common shell script tasks in an actual UNIX environment.

The UNIX Bourne shell, introduced by Stephen Bourne in 1977, is a foundational command-line interpreter known for its simplicity and powerful scripting capabilities. One of its advanced features is its robust scripting language, which supports control structures like loops (for, while, until), conditionals (if-then-else), and case statements. These constructs allow users to write complex scripts for automating tasks, such as batch processing or system administration. The shell’s ability to handle variables, including environment variables, enables dynamic configuration and data manipulation. Additionally, the Bourne shell’s support for command substitution (using backticks or $()) allows scripts to capture the output of commands and use it as input for others, enhancing flexibility in script design.
Another significant feature is the Bourne shell’s input/output redirection and piping capabilities, which provide fine-grained control over data flow. Redirection operators (>, <, >>) allow users to redirect command output to files or use files as input, while pipes (|) enable the output of one command to serve as the input for another, facilitating the creation of powerful command chains. The shell also supports file descriptors, allowing advanced manipulation of input and output streams, such as redirecting error messages (2>) separately from standard output. These features make the Bourne shell exceptionally suited for tasks requiring intricate data processing or integration of multiple commands, a hallmark of UNIX’s modular design philosophy.
The Bourne shell also excels in job control and signal handling, which are critical for managing processes in a UNIX environment. Users can run commands in the background (&), suspend processes, or bring them to the foreground, providing efficient multitasking within the shell. Signal handling allows scripts to trap and respond to system signals (e.g., SIGINT for interrupts), enabling graceful error handling or cleanup operations. Additionally, the shell’s support for functions allows reusable code blocks within scripts, improving modularity and maintainability. These advanced features, combined with its portability across UNIX systems, cemented the Bourne shell’s legacy as a cornerstone of shell scripting, influencing successors like Bash and KornShell.

Completing the course, you will be able to:

1. Create a shell script that can add and remove lines from a text file
2. Create a shell script that searches text files for a given pattern
3. Create a shell script that prints a subset of columns from a text file
4. Create a shell script that uses command line arguments and options
5. Identify and debug common problems found in shell scripts

In this course, you will learn and practice UNIX shell programming skills using various types of interactive tools:

1. Series of Images,
2. Diagrams,
3. Exercises and
4. Quizzes

The next lesson explains the prerequisites to this course.