Running Multi-Line Shell Code at Once From Single Prompt

Running multi-line shell code at once allows you to execute complex commands and scripts efficiently without typing each line individually. There are several techniques to accomplish this, from creating shell scripts to using command-line operators and here-documents.

Shell Script Method

The most common approach is creating a shell script file. Use any text editor to write your code and save it with a .sh extension:

#!/bin/bash
echo "Hello, World!"
echo "This is a shell script."

Execute the script using:

bash script.sh

Here-Document (EOF) Method

The here-document technique uses the << operator to pass multiple lines directly to a command:

bash << EOF
echo "Hello, World!"
echo "This is a shell script."
EOF

You can use here-documents with other commands as well:

cat << EOF
Line 1
Line 2
Line 3
EOF

Multi-Line Code Techniques

Line Continuation with Backslash

Use the backslash (\) character to continue commands across multiple lines:

echo "This is a very long command" \
     "that spans multiple lines"

For commands with multiple options:

command --option1 value1 \
        --option2 value2 \
        --option3 value3

Grouping with Parentheses

Parentheses group commands to execute as a single unit:

(echo "This is the first line"
 echo "This is the second line")

Function Blocks with Curly Braces

Create reusable command blocks using functions:

block_of_commands() {
    echo "This is the first command"
    echo "This is the second command"
}

block_of_commands

Command Chaining Operators

Using Semicolons

Execute multiple commands sequentially regardless of success or failure:

echo "First command"; echo "Second command"; pwd

Using Double Ampersand

Execute commands conditionally based on the success of previous commands:

test -e file.txt && echo "File exists"
command1 && command2 && command3

Using Double Pipe

Execute the next command only if the previous one fails:

command1 || echo "Command1 failed"

Practical Examples

Best Practices

• Use shell scripts for complex, reusable code that you'll run multiple times

• Use here-documents for quick, one-time multi-line execution without creating files

• Use backslashes to improve readability of long commands with many options

• Use && when you need commands to run only if previous ones succeed

• Use semicolons when you want all commands to run regardless of individual success/failure

Conclusion

Multiple techniques exist for running multi-line shell code at once, each suited to different scenarios. Shell scripts work best for complex, reusable code, while here-documents and command operators provide quick solutions for immediate execution. Choose the method that best fits your specific use case and readability requirements.