BASH Programming Training Course

The simplest script

Selecting the shell (magic number #!, Shebang)

Invoking the script

External and built-in commands

Key special characters

• Comments (#)
• End of line (;)
• Null statement (:)
• Input and output redirection (>, <, >>)
• Redirecting output
• Redirecting input
• Pipes (stream) (|)
• Running processes in the background (&)

Variables and Parameters

• Unsetting variables (unset)
• Variables with null values
• Storing results in variables (backticks ``)
• Parameter references ($ 0, $ #, $ 1, $ 2, $ 3 ...)
• Shift parameter
• Quoting.
• Escape characters (\)

Regular Expressions

Conditional Statements

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

Concluding a Script

The exit statement

Utilizing the script's execution status ($?)

Tests and Operators

• File test operators
• File type tests
• File attribute tests

Comparison Operators

• Arithmetic comparisons using the if command
• Integer comparison operators
• String comparison
• Complex comparisons (AND, OR)
• Nested comparison operators
• Assignment operators
• 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
• select menu

Features

sleep command

Troubleshooting: What to do if the script fails? (Debugging)