Bash/Shell Scripting

7.

Debugging and Best Practices

7.1.

Debugging Techniques

7.1.1.

Shell Debugging Options

7.1.1.1.

set -x (Execution Trace)

7.1.1.2.

set -v (Verbose Mode)

7.1.1.3.

set -e (Exit on Error)

7.1.1.4.

set -u (Unset Variable Error)

7.1.1.5.

set -o pipefail (Pipe Failure)

7.1.2.

Command-Line Debugging

7.1.2.1.

bash -x script.sh

7.1.2.2.

bash -n script.sh (Syntax Check)

7.1.3.

Static Analysis Tools

7.1.3.1.

7.1.3.2.

Installation and Usage

7.1.3.3.

Common Warnings and Fixes

7.1.4.

7.1.4.1.

Strategic echo Statements

7.1.4.2.

printf for Formatted Output

7.1.4.3.

Conditional Debug Output

7.1.4.4.

Debug Functions

7.1.5.

Interactive Debugging

7.1.5.1.

bash Debugger (bashdb)

7.1.5.2.

Step-by-Step Execution

7.2.

7.2.1.

Exit Status Codes

7.2.1.1.

Understanding Exit Codes

7.2.1.2.

Setting Custom Exit Codes

7.2.1.3.

Checking Command Success

7.2.2.

Error Detection

7.2.2.1.

Testing Command Results

7.2.2.2.

Validating Input

7.2.2.3.

File and Directory Checks

7.2.3.

Error Reporting

7.2.3.1.

Writing Error Messages

7.2.3.2.

7.2.3.3.

User-Friendly Messages

7.2.4.

Recovery Strategies

7.2.4.1.

Graceful Degradation

7.2.4.2.

7.2.4.3.

Fallback Options

7.3.

7.3.1.

Log File Management

7.3.1.1.

Creating Log Files

7.3.1.2.

7.3.1.3.

7.3.2.

7.3.2.1.

Adding Timestamps

7.3.2.2.

Date Formatting

7.3.3.

Structured Logging

7.3.3.1.

Log Format Standards

7.3.3.2.

Parsing Log Files

7.3.4.

7.3.4.1.

syslog Integration

7.3.4.2.

7.4.

Security Considerations

7.4.1.

Input Validation

7.4.1.1.

Sanitizing User Input

7.4.1.2.

Preventing Injection Attacks

7.4.1.3.

Validating File Paths

7.4.2.

File Permissions

7.4.2.1.

Setting Appropriate Permissions

7.4.2.2.

Temporary File Security

7.4.2.3.

Avoiding World-Writable Files

7.4.3.

Environment Security

7.4.3.1.

7.4.3.2.

Avoiding Dangerous Commands

7.4.3.3.

Privilege Escalation Prevention

7.4.4.

Secure Coding Practices

7.4.4.1.

Quoting Variables

7.4.4.2.

Using Full Paths

7.4.4.3.

7.5.

Scripting Best Practices

7.5.1.

Code Organization

7.5.1.1.

Script Structure

7.5.1.2.

Function Organization

7.5.1.3.

Configuration Separation

7.5.2.

7.5.2.1.

Inline Comments

7.5.2.2.

Function Documentation

7.5.2.3.

7.5.2.4.

7.5.3.

Naming Conventions

7.5.3.1.

7.5.3.2.

7.5.3.3.

7.5.3.4.

Consistent Style

7.5.4.

7.5.4.1.

Idempotent Scripts

7.5.4.2.

Error-Resistant Code

7.5.4.3.

Performance Considerations

7.5.5.

Common Pitfalls

7.5.5.1.

Unquoted Variables

7.5.5.2.

Filename Spaces

7.5.5.3.

Useless Use of cat

7.5.5.4.

Bashisms in sh Scripts

7.5.5.5.

Word Splitting Issues

7.5.6.

7.5.6.1.

Unit Testing Frameworks

7.5.6.2.

Integration Testing

7.5.6.3.

Test-Driven Development

7.5.6.4.

Automated Testing

7.5.7.

Version Control

7.5.7.1.

Git for Scripts

7.5.7.2.

Branching Strategies

7.5.7.3.

Release Management

7.5.8.

7.5.8.1.

Installation Scripts

7.5.8.2.

Configuration Management

7.5.8.3.

Environment-Specific Settings

7.5.8.4.

Rollback Procedures

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6. Advanced Scripting Techniques

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1. Introduction to the Shell and Scripting