command Command

command [OPTIONS] COMMAND [ARGUMENTS...] command -v COMMAND command -V COMMAND

# Create an alias alias ls='ls --color=auto -la' # Use the alias ls # Bypass the alias command ls # Create a function cd() { builtin cd "$@" && ls } # Use the function cd /tmp # Bypass the function command cd /tmp

# Show command path (like which) command -v ls command -v grep command -v python3 # Show detailed command information command -V ls command -V cd command -V alias # Check if command exists if command -v docker >/dev/null 2>&1; then echo "Docker is installed" else echo "Docker is not installed" fi

# Show current PATH echo $PATH # Use command with custom PATH export PATH="/custom/bin:$PATH" command -v ls # Use command with default PATH command -p -v ls # Execute with default PATH command -p ls /bin

#!/bin/bash # Ensure we use actual commands, not aliases safe_copy() { local src="$1" local dest="$2" # Use actual cp command, not any alias command cp "$src" "$dest" } # Ensure we use actual rm command safe_remove() { local file="$1" # Confirm before deletion read -p "Delete $file? (y/N): " confirm if [[ $confirm =~ ^[Yy]$ ]]; then command rm "$file" fi } # Use functions safe_copy "source.txt" "backup.txt" safe_remove "temp.txt"

#!/bin/bash check_command() { local cmd="$1" if command -v "$cmd" >/dev/null 2>&1; then echo "✓ $cmd is available at: $(command -v "$cmd")" command -V "$cmd" else echo "✗ $cmd is not available" return 1 fi echo } # Check required commands required_commands=("git" "docker" "python3" "node" "npm") echo "Checking required commands..." for cmd in "${required_commands[@]}"; do check_command "$cmd" done # Check optional commands optional_commands=("vim" "emacs" "code" "curl" "wget") echo "Checking optional commands..." for cmd in "${optional_commands[@]}"; do check_command "$cmd" || echo "Consider installing $cmd" done

#!/bin/bash debug_command() { local cmd="$1" echo "=== Debugging command: $cmd ===" # Check if it's an alias if alias "$cmd" 2>/dev/null; then echo "Type: Alias" alias "$cmd" fi # Check if it's a function if declare -f "$cmd" >/dev/null 2>&1; then echo "Type: Function" declare -f "$cmd" fi # Check if it's a built-in if type -t "$cmd" 2>/dev/null | grep -q "builtin"; then echo "Type: Built-in" fi # Show actual command location echo "Actual command location:" command -V "$cmd" # Show what would be executed echo "What gets executed:" type "$cmd" echo "========================" } # Debug common commands debug_command "ls" debug_command "cd" debug_command "grep"

#!/bin/bash # System backup script using command to ensure reliability backup_system() { local backup_dir="/backup/$(date +%Y%m%d)" # Ensure we use actual commands command mkdir -p "$backup_dir" # Backup important directories echo "Backing up /etc..." command tar -czf "$backup_dir/etc.tar.gz" /etc echo "Backing up /home..." command tar -czf "$backup_dir/home.tar.gz" /home echo "Backing up /var/log..." command tar -czf "$backup_dir/logs.tar.gz" /var/log # Set permissions command chmod 600 "$backup_dir"/*.tar.gz # Verify backups echo "Backup files created:" command ls -lh "$backup_dir" # Clean old backups (keep last 7 days) command find /backup -name "20*" -type d -mtime +7 -exec rm -rf {} \; echo "Backup completed: $backup_dir" } # Check prerequisites for cmd in mkdir tar chmod ls find rm; do if ! command -v "$cmd" >/dev/null 2>&1; then echo "Error: Required command '$cmd' not found" exit 1 fi done backup_system

#!/bin/bash setup_dev_environment() { echo "Setting up development environment..." # Check required tools required_tools=("git" "curl" "wget" "unzip" "tar") for tool in "${required_tools[@]}"; do if ! command -v "$tool" >/dev/null 2>&1; then echo "Installing $tool..." case $(command -v apt-get || command -v yum || command -v brew) in *apt-get*) sudo apt-get update && sudo apt-get install -y "$tool" ;; *yum*) sudo yum install -y "$tool" ;; *brew*) brew install "$tool" ;; *) echo "Please install $tool manually" ;; esac else echo "✓ $tool is already installed" fi done # Setup Git if not configured if ! command git config --global user.name >/dev/null 2>&1; then read -p "Enter your Git username: " git_user read -p "Enter your Git email: " git_email command git config --global user.name "$git_user" command git config --global user.email "$git_email" fi # Create development directories command mkdir -p ~/dev/{projects,tools,scripts} echo "Development environment setup complete!" } setup_dev_environment

#!/bin/bash secure_file_operations() { local source_file="$1" local dest_dir="$2" # Validate inputs if [[ ! -f "$source_file" ]]; then echo "Error: Source file does not exist" return 1 fi if [[ ! -d "$dest_dir" ]]; then echo "Error: Destination directory does not exist" return 1 fi # Use command to ensure we use actual binaries echo "Copying file securely..." # Copy with verification if command cp "$source_file" "$dest_dir/"; then echo "File copied successfully" # Verify copy if command cmp "$source_file" "$dest_dir/$(basename "$source_file")" >/dev/null 2>&1; then echo "Copy verified successfully" # Set secure permissions command chmod 600 "$dest_dir/$(basename "$source_file")" # Show final permissions command ls -l "$dest_dir/$(basename "$source_file")" else echo "Error: Copy verification failed" command rm "$dest_dir/$(basename "$source_file")" return 1 fi else echo "Error: Copy operation failed" return 1 fi } # Usage secure_file_operations "sensitive.txt" "/secure/backup"