Introduction to POSIX Shell Scripts * What is a shell script? * Script execution * The subprocess environment * Shell features Shell Scripting * Which shell? * Recommended script format * Planning to write a shell script * Portability issues Variables * Variables * Displaying and using variables * Concatenation and substrings * Other sources of data for variables User Input * Reading user input * Positional parameters * Creating positional parameters * Conditional substitution * External influences Designing Program Output * Variable attributes * Formatted data * Cursor positioning and terminal echo Shell Arithmetic * Creating integer-only variables * Base10 and others * Working with arithmetic operators and data Branches and Logic Testing * Logic testing * Conditional operators * Multiway decision branching and the case statement Shell Patterns * Basic expressions * More complex patterns * Pattern combinations Program Loops * The while loop * The until loop * The for loop * Breaking out of a loop * Continue and exit commands * The select loop The getopts Command * Processing arguments * The getopts and OPTARG variable * The OPTIND variable Array Variables * Substituting and counting * Using integer variables as element numbers Functions and Function Libraries * Displaying current shell functions * Declaring and using functions * Variable scope * Function libraries and recursion Managing Input and Output * File descriptors * Reading and writing using file descriptors * Redirecting, parameter lists, and here documents * Creating parameter lists from input lines Traps and Signals * Common signals * The trap and stty commandsRegular Expressions * Regular expressions * Metacharacters * The grep command Introduction to awk * Record processing * Pattern matching and printing * Relational expressions * awk variables Variables, Strings, and Arithmetic Operations * awk user-defined variables * Environment variables * Arithmetic operations * String manipulation * Formatted output * Command line arguments awk Flow Control * Conditional if, while, and for loops * Arrays * getline, next, and exit * Processing arrays * Associative arrays Stream Editing with sed * Substituting text * Deleting and printing lines * Reading and writing files * Multiple sed editor functions