Here strings (<<<) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a here string (<<<) in bash scripting?

A here string is a way to pass a short string as input to a command directly, using <<< followed by the string. It acts like a small input file.

intermediate

How does a here string differ from a here document in bash?

A here string passes a single string as input, while a here document passes multiple lines or a block of text. Here strings use <<< and here documents use <<.

beginner

Example: What does this command do? <br>grep 'hello' <<< 'hello world'

It searches for the word 'hello' in the string 'hello world' passed as input via the here string. It will output 'hello world' because 'hello' is found.

beginner

Can you use variables with here strings? Show an example.

Yes. For example: <br>name='Alice'<br>grep 'Alice' <<< "$name" <br>This passes the value of the variable 'name' as input.

intermediate

Why might you choose a here string over echo piping?

Here strings are simpler and faster for short input because they avoid creating a pipe. They are cleaner for passing small strings directly to commands.

What symbol is used to create a here string in bash?

A >>

B <<

C <

D <<<

The here string uses the symbol <<< to pass a string as input.

Which of these commands uses a here string correctly?

A cat <<< 'Hello World'

B cat << 'Hello World'

C cat < 'Hello World'

D cat >> 'Hello World'

cat <<< 'Hello World' uses a here string to pass 'Hello World' as input.

What will this command output? <br>grep 'test' <<< 'this is a test'

A this is a test

B test

C No output

D Error

The grep finds 'test' in the input string and outputs the whole line.

Can here strings handle multi-line input?

A Yes, multiple lines

B Only if quoted

C No, only single line

D Only with special flags

Here strings pass a single string, usually one line. For multiple lines, use here documents.

Which is a benefit of using here strings?

A Better for large files

B Simpler syntax for short input

C Creates temporary files

D Runs commands faster than normal

Here strings provide a simple way to pass short input strings directly.

Explain what a here string (<<<) is and how it is used in bash scripting.

Think about how you give a command a quick input string without a file.

Describe a practical example where a here string is useful and why it might be preferred over echo piping.

Consider searching text or feeding a small string to a command.