How do I prevent bash $ substitution?

Question

I'm trying to preserve $if below and
would like the following to output
$if

bash is getting in the way by doing
$ substitution

$ sed -e 's:\\$:\\$:g' <<ENDOFFILE  
> $if  
> ENDOFFILE

or

$ tr '$' '\$' <<ENDOFFILE  
> $if  
> ENDOFFILE

Is there a way to preserve $keywords
to stdout without explicitly escaping
them out in stdin?

Should I switch to another shell before attempting this?

Have you tried putting '$if' in single quotes in the text block? — Matt Simmons, Aug 03 '10 at 19:32

score 8 · Accepted Answer · answered Aug 03 '10 at 19:53

8

I'm not sure what you are trying to do but bash is performing parameter expansion in your here document because the delimiter ENDOFFILE. If you were to change it to 'ENDOFFILE' bash would not expand.

answered Aug 03 '10 at 19:53

Mark Wagner

17,764
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1

Why does this work and the unquoted ENDOFFILE does not? – Aug 03 '10 at 20:07
2

@Dragos: It's [by-design]. If you look in `man bash` you'll see that it's a documented feature. – Dennis Williamson Aug 03 '10 at 20:43

score 0 · Answer 2 · answered Aug 03 '10 at 19:50

0

Not sure what exactly you are trying to do here, but you can use tr and the octal value of $ which is 044. Experiment with this:

echo 'ab$de' | tr \\044 C

answered Aug 03 '10 at 19:50

jftuga

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Test your recommendation. He's trying to escape a variable via STDIN using string manipulation. You are escaping in the echo. – Warner Aug 03 '10 at 19:52

How do I prevent bash $ substitution?

2 Answers2