Advanced Scripting Techniques

Accessing Arguments ($1, $2, ...)

Number of Arguments ($#)

All Arguments ($@ vs $*)

shift Command

Processing Variable Arguments

Basic getopts Usage

Short Options

Options with Arguments

Error Handling

OPTARG and OPTIND Variables

Manual Parsing

Using getopt Command

Help Functions

Error Messages

Exit Codes

Running Commands in Background (&)

Disowning Processes (disown)

nohup Command

Listing Jobs (jobs)

Foreground Jobs (fg)

Background Jobs (bg)

Job Specifications (%1, %2, etc.)

Process IDs ($$, $!)

Parent Process ID ($PPID)

ps Command

pgrep and pkill

Exit Codes

Signals

Inter-Process Communication

wait Command

Waiting for Specific Processes

Timeout Handling

Signal Types

Signal Numbers

Default Signal Handlers

Basic Syntax

Setting Signal Handlers

Removing Traps

SIGINT (Interrupt)

SIGTERM (Terminate)

SIGKILL (Kill)

SIGHUP (Hangup)

SIGUSR1 and SIGUSR2

EXIT Pseudo-signal

Cleanup on Exit

Graceful Shutdown

Temporary File Management

Lock File Handling

Creating Isolated Environments

Variable Scope in Subshells

Directory Changes in Subshells

Exit Status from Subshells

Grouping Commands in Current Shell

Redirection with Command Groups

Conditional Command Groups

${parameter}

Parameter Existence

${parameter:-default}

${parameter:=default}

${parameter:?error}

${parameter:+alternate}

${#parameter}

${parameter:offset}

${parameter:offset:length}

Remove Shortest Match (${parameter#pattern})

Remove Longest Match (${parameter##pattern})

Remove from End (${parameter%pattern})

Remove from End Longest (${parameter%%pattern})

Replace First Match (${parameter/pattern/string})

Replace All Matches (${parameter//pattern/string})

Replace at Beginning (${parameter/#pattern/string})

Replace at End (${parameter/%pattern/string})

Uppercase (${parameter^^})

Lowercase (${parameter,,})

Capitalize (${parameter^})

Sequence Generation ({1..10})

String Lists ({a,b,c})

Nested Braces

Home Directory (~)

User Home Directories (~user)

Wildcards (*, ?, [...])

Extended Globbing

Recursive Globbing (**)

Dotglob Option

Modern Syntax $()

Legacy Syntax ``

Nested Substitutions

Basic Syntax $((...))

Variables in Arithmetic

Complex Expressions