BASH Programming Training Course

The simplest script

Choosing the shell (magic number #!, Shebang)

Executing the script

External and built-in commands

Special characters

• Comment (#)
• End of Line (;)
• Null statement (:)
• Input/output redirection (>, <, >>)
• Output redirection
• Input redirection
• Pipe (|)
• Background process execution (&)

Variables and Parameters

• Variable destruction (unset)
• Variables with null values
• Storing results in variables (backticks ``)
• Parameter retrieval ($0, $#,$1, $2, $3...)
• Manual shifting
• Quoting
• Escape character (\)

Regular Expressions

Conditional statements

• The if/then construct
• The if/then/else construct
• Nesting if statements
• The if/elif construct
• Case statements
• Operators
• Logical operators: AND, OR (&&, ||)
• The test command

Completing the script

The exit statement

Utilising the program's exit status in a script ($?)

Tests and Operators

• Text file operators
• File type tests
• File attribute tests

Comparison operators

• Arithmetic comparison using the if command
• Integer comparison operators
• String comparison
• Complex comparisons (AND, OR)
• Nesting comparison operators
• The assignment operator
• Arithmetic operators
• Bitwise operators
• Logical operators
• Numeric constants

Loops

• The for/in loop
• The seq command
• The while loop
• The until loop
• Loop control (break, continue)

Text Processing

• head, tail commands
• Sort, Uniq, Expand, Unexpand
• Cut, Paste, Join, Wc, Tr

Text search (grep)

Stream Editor (sed)

Interactive programs

• read command
• User select

Features

sleep command

Troubleshooting: What if the script fails? (debugging)