Introduction to Bash 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

• 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 commands Regular 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