Shell STDIN重定向三个反引号

Question

Motivation

I have a Markdown backtick codeblock and I would like to insert it into a list item. I tried using awk with STDIN redirection for fun. I ran into the following problem.

Problem

I adapted from Tutorials Point 's example to count the number of lines of a Markdown codeblock.

$ wc -l << EOF
```
codeblock
```
EOF

• Expected output: 3

• Actual output:

   zsh: command not found: codeblock 1 

How to get the shell parse an odd number of backticks in STDIN?

Thanks for reading.

Answer 1

Backticks are for command substitution , and command substitutions are expanded in here documents . You should either quote EOF -this will disable all expansions-, or escape those backticks.

$ wc -l << 'EOF'
```
codeblock
```
EOF

3
$ 
$ wc -l << EOF 
\`\`\`
codeblock
\`\`\`
EOF

3