BASH Programming Training Course

The simplest script

Choosing the shell (magic number #!, Shebang)

Calling the script

External and built-in commands

Special characters

• Comment (#)
• End of Line (;)
• Empty statement (:)
• Redirection of input and output (>, <, >>)
• Redirecting output
• Redirection of input
• Stream (|)
• Starting a process in the background (&)

Variables and Parameters

• Destruction of variables (unset)
• Variables with null values
• Saving results to a variable (backquotes ``)
• Parameter requests ($0, $#,$1, $2, $3...)
• Manual shift
• 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 (&&, ||)
• Test command

Completing the script

The exit statement

Using the program completion status in a script ($?)

Tests and Operators

• Text file operators
• Tests for file types
• Tests for file attributes

Comparison operators

• Comparing arithmetic using the if command
• Integer comparison operators
• Comparing strings
• 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

If the script does not work? (Debugging)