Bug #17126: String#gsub fails to escape single quote for shell

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: 2.7.1
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN

[AndyMaleh (Andy Maleh)]

Hi, I don't know if I'm misunderstanding how String#gsub works, but I encountered an issue in the Ruby "git" gem with escaping single quotes for shell, which I fixed and contributed back.

I thought I'd report here too since it was caused by Ruby String#gsub malfunctioning, just in case there is a bug in Ruby.

Description:

When calling String#gsub("'", "'\\''") on a String that contains a single-quote (e.g. "Hello ' World"), it is duplicating the substring following the single-quote in the returned String instead of simply replacing the single-quote with escaped single quotes.

Code to Demonstrate Problem:

"Hello ' World".gsub('\'', '\'\\\'\'')

or

"Hello ' World".gsub("'", "'\\''")

or

"Hello ' World".gsub(/'/, "'\\''")

Output:

 => "Hello ' World' World"

Expected Output:

 => "Hello '\'' World"

In fact, I tested this same regex replacement in Java and got the expected output above.

I look forward to hearing back about this puzzling problem.

Perhaps it is not a bug and I am just misunderstanding how String#gsub works in Ruby as I noticed it behaves the same exact way in JRuby too.

Best regards,

Andy Maleh

[AndyMaleh (Andy Maleh)]

• Subject changed from String#gsub fails to escape single quote to String#gsub fails to escape single quote for shell
• Description updated (diff)

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Closed

\' means something special in a sub/gsub replacement string, see the documentation for details: https://docs.ruby-lang.org/en/2.7.0/String.html#method-i-gsub

As the documentation explains, use four backslashes:

puts "Hello ' World".gsub(/'/, "'\\\\''")
# Output:
# Hello '\'' World

[AndyMaleh (Andy Maleh)]

Got it. I missed that completely in the documentation, thinking it wasn't related to our use of \'.

Thanks a lot for explaining and for supporting the Ruby programming language in the open-source community.