Mastering BASH Scripts

Day 1

Introduction and Revision

• Command-line structure
• Shell interpretation
• Filename expansion
• Variable and command expansions
• Quoting
• Redirection
• Here documents
• Pipes

Using BASH

• The Bash story (in brief)
• Bash personalities
• Shell options
• Bash shell options
• Start-up files
• Some shell variables
• Aliases and functions
• Command-line recall and editing
• Navigation for the impatient
• echo and help

Shell Scripts

• Command types
• Creating shell scripts
• Creating processes
• The exec command
• Exit status
• Using # in shell scripts
• Running shell scripts
• BASH_ENV
• Command groups and sub-shells

Handling Variables

• Legal variable names
• Creating variables
• The read command
• Exporting variables
• Special characters
• Checking the environment
• eval

Parameters and Friends

• Positional parameters
• Access to positional parameters
• $*, $@, and $#
• Changing positional aparmeters
• $* versus $@
• Other special variables

Behaviour Therapy

• Sending signals,
• Receiving signals and the trap command
• Shell tracing methods
• Tracing shell expansions
• DEBUG and ERR traps
• Dry run of a script
• The script command
• Error messages are your friends

Day 2

Flow Control

• Testing commands
• ‘if’ statements
• ‘while’ and ‘until’ loops
• Bourne shell test command
• Korn shell test command
• Bourne and Korn syntax compared
• Numeric tests

Variable Expansion

• Extracting a sub-string
• Deleting a sub-string
• Editing sub-strings
• Test and set/exit expansions
• The colon command

Lofty Variables

• Variable attributes
• Compound assignments
• Arithmetic conditionals
• Working with floating-point

More Loops

• List processing – ‘for’ loop
• Processing positional parameters
• ‘break’ and ‘continue’
• Infinite loops
• The ‘select’ loop
• Reading in a loop from a file
• Reading in a loop from a program (process substitution)

Sophisticated Tests

• Statement short-cuts
• I/O redirection with if-then-fi
• The ‘case’ statement
• case flow control – Bash 4
• Shell pattern matching
• Extended pattern operators
• Locales and character classes

Using Functions

• Functions vs. scripts
• Creating functions
• Listing and removing functions
• Function parameters and return values
• Local and global variables
• Where to store functions
• Exported functions
• Using external function libraries

Day 3

Professional Scripts

• Parsing script options with getopts
• Handling errors
• Formatting output – printf
• Tips for shell programmers: programming for change
• Tips for shell programmers: programming for performance

Handling Arrays

• Arrays: the concepts
• Bash array syntax
• Array syntax gotchas
• Initialising arrays
• Appending to an array
• Finding array limits
• Using read with an array
• Using mapfile/readarray
• Associative arrays

Advanced IO

• The concepts
• Using file descriptors
• Block redirection
• Named pipes (FIFOs)
• Process substitution

Basic sed

• Running sed
• Basic regular expressions
• sed line addressing

Basic awk

• The awk programming model
• awk variables
• awk opeators
• Comparing awk with shell constructs

• Delegates should have a good working knowledge of Linux or UNIX systems, which includes a working knowledge of UNIX commands and utilities. This can be gained by attending our UNIX Fundamentals or Linux Essentials courses
• Delegates should also have a practical understanding of programming concepts such as variables, and decision-making constructs.