Bug #8512: gsub() works incorrect

• Status: Rejected
• Priority: Normal
• Assignee: -
• Target version: -
• ruby -v: ruby 2.0.0p195 (2013-05-14) [i386-mingw32]
• Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN

[galnaktar (Oleg K)]

irb(main):005:0> "\".gsub("\", "\\").length
=> 1
irb(main):006:0> "\".gsub("\", "XX").length
=> 2

bug is duplicated with rejected bug #8511

[Eregon (Benoit Daloze)]

• Status changed from Open to Rejected

This is due to Regexp replace syntax and literal strings.

In literal strings, you need two \ to produce one \ character (a single is the start of an escape character like \t, \n, ...).
And in Regexp replacement strings, you need to escape the \ (a single one is the beginning of a special replacement sequence like \1,&,...).
So that makes 4 \ for one produced in literal replacement strings:

"\".gsub("\", "\\").length
=> 1
"\".gsub("\", "\\\\").length
=> "\\"

Not so nice, but definitely expected behavior.

[Eregon (Benoit Daloze)]

This should be documented in Regexp's overview though.

[Hanmac (Hans Mackowiak)]

=begin

the docs says:

((If replacement is a String it will be substituted for
the matched text. It may contain back-references to the pattern's capture
groups of the form \\d, where d is a group number, or \\k, where n is
a group name. If it is a double-quoted string, both back-references must be
preceded by an additional backslash.))

so you need more "\" in your string
=end

[galnaktar (Oleg K)]

Hanmac (Hans Mackowiak) wrote:

=begin

the docs says:

((If replacement is a String it will be substituted for
the matched text. It may contain back-references to the pattern's capture
groups of the form \\d, where d is a group number, or \\k, where n is
a group name. If it is a double-quoted string, both back-references must be
preceded by an additional backslash.))

so you need more "\" in your string
=end

Thanks for the explanation.

[phluid61 (Matthew Kerwin)]

For the record, you can also use the hash or block replacement forms, because those doesn't use regexp back-references:

"\".gsub("\", "\"=>"\\") #=> "\\"
"\".gsub("\") { "\\" } #=> "\\"