如何编写Shell脚本实现目录检查、切换或创建（使用nano编辑器）

Hey there, here's a practical shell script that does exactly what you need—plus I'll walk you through writing it with the nano editor step by step.

The Script Code #

First, let's create a flexible script that takes the target directory and file as arguments (so you can reuse it for different paths). Save this as dir_file_check.sh:

#!/bin/bash

# Check if both directory and file arguments are provided
if [ $# -ne 2 ]; then
    echo "Usage: $0 <target_directory> <target_file>"
    exit 1
fi

TARGET_DIR="$1"
TARGET_FILE="$2"

# Check if the directory exists; if not, create it
if [ -d "$TARGET_DIR" ]; then
    echo "Directory $TARGET_DIR exists, switching to it..."
    cd "$TARGET_DIR" || exit 1  # Exit if cd fails (e.g., permission issues)
else
    echo "Directory $TARGET_DIR does not exist, creating it..."
    mkdir -p "$TARGET_DIR" || exit 1  # -p creates parent directories if needed
    cd "$TARGET_DIR" || exit 1
fi

# Check if the specified file does NOT exist
if [ ! -f "$TARGET_FILE" ]; then
    echo "⚠️  File $TARGET_FILE does not exist in $(pwd)"
    # You can add additional actions here, like creating an empty file:
    # touch "$TARGET_FILE"
    # echo "Created empty file $TARGET_FILE"
else
    echo "File $TARGET_FILE exists in $(pwd)"
fi

Let's break down what this does: #

• #!/bin/bash: Declares this as a bash script to ensure consistent behavior across environments
• Argument check: Makes sure you pass both a directory and file path when running the script (avoids errors from missing inputs)
• [ -d "$TARGET_DIR" ]: Checks if the target directory already exists
• mkdir -p "$TARGET_DIR": Creates the directory (and any missing parent directories, if needed) if it doesn't exist
• cd "$TARGET_DIR" || exit 1: Switches to the target directory, and exits the script immediately if the switch fails (e.g., due to permission issues)
• [ ! -f "$TARGET_FILE" ]: Checks if the specified file does not exist—you can uncomment the touch lines if you want to automatically create an empty file when it's missing

Writing the Script with Nano #

Nano is a simple, terminal-based text editor that's perfect for writing quick scripts. Here's how to use it:

1. Open nano and create the script file:
   Run this command in your terminal:

   nano dir_file_check.sh
   

   This will open a blank nano editor window ready for input.

2. Enter the script code:
   Copy the script above and paste it into the nano window (right-click to paste if you're using a GUI terminal, or use Ctrl+Shift+V on most Linux/macOS systems).

3. Save and exit:

   • Press Ctrl+O (that's the letter O, not zero) to save the file. You'll see a prompt asking for the filename—just press Enter to confirm.
   • Press Ctrl+X to exit the nano editor.

4. Make the script executable:
   Before you can run it, you need to grant execution permissions:

   chmod +x dir_file_check.sh
   

5. Run the script:
   Use this format to run it, replacing the example paths with your actual directory and file:

   ./dir_file_check.sh /home/yourname/my_project /home/yourname/my_project/config.txt
   

内容的提问来源于stack exchange，提问作者Spinescream