Start Coding

Subjects

JAVASCRIPTHTMLCSSPYTHONSQLJAVACPPCSHARPPHPTYPESCRIPTCRUBYGOSWIFTKOTLINRUSTRBASHSCALAOBJECTIVE-CDARTPERLLUAMATLABXMLJSONMARKDOWNASSEMBLYLATEXYAMLSOLIDITYBLOCKCHAIN

Topics

Introduction to Bash

What is BashBash vs. other shellsInstalling BashBash environment setupBash command structure

Bash Basics

Bash command line interfaceBash shell promptBash basic commandsBash file system navigationBash file manipulationBash input/output redirectionBash pipesBash command historyBash tab completionBash wildcards and globbing

Bash Variables and Data Types

Bash variables declarationBash environment variablesBash variable scopeBash string manipulationBash arraysBash arithmetic operations

Bash Control Structures

Bash if-else statementsBash case statementsBash for loopsBash while loopsBash until loopsBash break and continueBash select statements

Bash Functions

Bash function declarationBash function parametersBash function return valuesBash local variablesBash recursive functions

Bash Input and Output

Bash read commandBash echo commandBash printf commandBash here documentsBash process substitution

Bash File Operations

Bash file testingBash file permissionsBash file comparisonBash file archiving and compression

Bash Text Processing

Bash grep commandBash sed commandBash awk commandBash cut commandBash sort commandBash uniq commandBash regular expressions

Bash Scripting

Bash script structureBash shebangBash script executionBash command line argumentsBash exit statusBash debugging techniquesBash error handling

Bash Advanced Topics

Bash process managementBash job controlBash signal handlingBash trapsBash subshellsBash command substitutionBash parameter expansionBash brace expansionBash tilde expansionBash aliasesBash options and settings

Bash Best Practices

Bash script organizationBash coding styleBash performance optimizationBash security considerationsBash script portability

Bash and System Administration

Bash system monitoringBash user managementBash network operationsBash cron jobsBash log file analysis

Bash Signal Handling

Signal handling is a crucial aspect of Bash scripting that allows you to manage and respond to various system signals. These signals are used for inter-process communication and can significantly impact the behavior of your scripts.

What are Signals?

Signals are software interrupts sent to a program to indicate that an important event has occurred. The events can vary from user requests to exceptional runtime occurrences. Some common signals include:

  • SIGINT (2): Interrupt from keyboard (Ctrl+C)
  • SIGTERM (15): Termination signal
  • SIGKILL (9): Kill signal (cannot be caught or ignored)
  • SIGHUP (1): Hangup detected on controlling terminal

Handling Signals in Bash

Bash provides the trap command to handle signals. The basic syntax is:

trap 'commands' SIGNALS

Here, 'commands' is the code to execute when the specified SIGNALS are received.

Example: Handling SIGINT

#!/bin/bash

trap 'echo "Ctrl+C pressed. Exiting..."; exit 1' SIGINT

echo "This script will run until you press Ctrl+C"
while true; do
    sleep 1
done

In this example, the script will continue running until the user presses Ctrl+C, at which point it will display a message and exit gracefully.

Ignoring Signals

You can also use trap to ignore specific signals:

trap '' SIGINT

This will cause the script to ignore the SIGINT signal (Ctrl+C).

Resetting Signal Handlers

To reset a signal handler to its default behavior, use:

trap - SIGNAL

Best Practices

  • Always handle SIGINT and SIGTERM to ensure graceful script termination.
  • Use signal handling for cleanup operations, such as removing temporary files.
  • Be cautious when ignoring signals, as it may lead to unexpected behavior.
  • Remember that SIGKILL cannot be caught or ignored.

Related Concepts

To further enhance your Bash scripting skills, consider exploring these related topics:

By mastering signal handling, you'll be able to create more robust and responsive Bash scripts that can gracefully handle various system events and user interactions.