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Prevent expressions enclosed in backticks from being evaluated in heredocs

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Original source (stackoverflow.com)
Tags: bash shell-scripting heredoc stackoverflow.com
Clipped on: 2016-05-05

I have a text like this:

foo bar
`which which`

If I do this using heredoc, I get a blank file:

➜  ~  echo <<EOT > out
heredoc> foo bar
heredoc> `which which`
heredoc> EOT
➜  ~  cat out

➜  ~

How can I do this?

Edit

Oh sorry, I meant to do cat. Problem is that it writes this to the file: which: shell built-in command, ie, evaluations backticks. Any way to do this without evaluating?

With cat, I get

➜  ~  cat <<EOT > out
heredoc> foo bar
heredoc> `which which`
heredoc> EOT
➜  ~  cat out
foo bar
which: shell built-in command
➜  ~

I don't want which which to be evaluated.

asked Oct 29 '12 at 12:58
Image (Asset 3/4) alt=
user1527166
1,0093916
up vote 12 down vote accepted

Quote the label to prevent the backticks from being evaluated.

$ cat << "EOT" > out
foo bar
`which which`
EOT

$ cat out
foo bar
`which which`
answered Oct 29 '12 at 13:02
Image (Asset 4/4) alt=
dogbane
126k39219308
   upvote
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Oh sorry, I meant to do cat. Problem is that it writes this to the file: which: shell built-in command, ie, evaluations backticks. Any way to do this without evaluating? – user1527166 Oct 29 '12 at 13:04
   upvote
  flag
Quote the label to prevent the backticks from being evaluated. – dogbane Oct 29 '12 at 13:06
   upvote
  flag
Perfect, thank you :) – user1527166 Oct 29 '12 at 13:10
2 upvote
  flag
FYI this will also disable other bash expression (such as variable evaluation) from occurring. To just disable backtick evaluation you can escape the backticks by adding a backslash, e.g. '\`' – Keith Feb 6 '15 at 20:43

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