How does the leading dollar sign affect single quotes in Bash?

bash quotes double-quotes single-quotes
user1206899 picture user1206899 · Aug 15, 2012 · Viewed 18.9k times · Source

I need to pass a string to a program as its argument from the Bash CLI, e.g

program "don't do this"

The string may include any character like '$', '\', etc. and I don't want Bash to do any modification. So I think about using single quotes.

However the following does not work:

 program 'don\'t do this'            //escape doesn't work in single quote

While the following two works:

 program $'dont\'t do this'          //seems fine, but any other side effects?
 program 'dont'\''do this'           //breaking into 3 parts

The first approach seems better in that it acquires less pre modification (put the dollar symbol in front and substitute every \ to \\), but I don't know what else the DOLLAR SIGN might do.

I've really googled this but I can't find what I need...

Answer

Ignacio Vazquez-Abrams picture Ignacio Vazquez-Abrams · Aug 15, 2012

It causes escape sequences to be interpreted.

$ echo $'Name\tAge\nBob\t24\nMary\t36'
Name    Age
Bob     24
Mary    36

After those sequences are expanded, the result is single-quoted, as if the dollar sign had not been present.

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