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Executable Shell Scripts (.sh) - A Comprehensive Guide

Basic Structure​

1. Create the Script File​

touch myscript.sh

2. Add Shebang Line​

The first line should specify the interpreter:

#!/bin/bash

Making Scripts Executable​

Method 1: Using chmod​

chmod +x myscript.sh

Method 2: Specific Permissions​

chmod 755 myscript.sh

Running Scripts​

Method 1: Direct Execution​

./myscript.sh

Method 2: Using bash​

bash myscript.sh

Script Writing Techniques​

Here Document (EOF) Example​

cat << 'EOF' > myscript.sh
#!/bin/bash
echo "Hello World"
echo "This is a multi-line script"
EOF

Basic Script Template​

#!/bin/bash

# Script description
# Author: Your Name
# Date: YYYY-MM-DD

# Variables
VARIABLE_NAME="value"

# Main logic
echo "Starting script..."

# Your commands here

echo "Script completed."

Best Practices​

  1. Always include shebang line
  2. Add comments for documentation
  3. Use meaningful variable names
  4. Include error handling
  5. Test for required dependencies
  6. Use proper file permissions

Common Permission Meanings​

  • 755: Owner can read/write/execute, others can read/execute
  • 700: Only owner can read/write/execute
  • 644: Owner can read/write, others can read
  • 600: Only owner can read/write

Script Execution Troubleshooting​

If you encounter "Permission denied":

  1. Check file permissions
  2. Verify script location
  3. Ensure correct shebang
  4. Check file ownership

Example Script with Error Handling​

#!/bin/bash

# Exit on error
set -e

# Error handling function
handle_error() {
    echo "Error occurred in script at line: $1"
    exit 1
}

trap 'handle_error $LINENO' ERR

# Script logic here
echo "Script running..."