regex bug?

[Zach Dennis]

key = "file"
attrib = "\\Applications\\4Dapp\\Chess\\"
command = "xcopy [file] /y /s /e i:\\source\\"
command.gsub!( /\[#{key}\]/ , "#{attrib}" )
puts command
=> "xcopy \\ApplicationsDapp\\Chess\\ /y /s /e i:\\source\\"



It should be:

=> "xcopy \\Applications\\4Dapp\\Chess\\ /y /s /e i:\\source\\"


Any idea why it keeps stealing my \4?

Zach

 

[Hal Fulton]

key = "file"
attrib = "\\Applications\\4Dapp\\Chess\\"
command = "xcopy [file] /y /s /e i:\\source\\"
command.gsub!( /\[#{key}\]/ , "#{attrib}" )
puts command
=> "xcopy \\ApplicationsDapp\\Chess\\ /y /s /e i:\\source\\"



It should be:

=> "xcopy \\Applications\\4Dapp\\Chess\\ /y /s /e i:\\source\\"


Any idea why it keeps stealing my \4?

It recognizes \4 as meaning the fourth submatch of the
last regex, or something to that effect.

Double escaping or something should fix it.

Hal

 

[John W. Long]

-----"Zach Dennis" wrote:-----

command.gsub!( /\[#{key}\]/ , "#{attrib}" )

replace this line with:
command.gsub!( /\[#{key}\]/ , "#{Regexp::quote(attrib)}" )

Any idea why it keeps stealing my \4?

Because in gsub terms \4 represents the forth grouping:

"123412341234".gsub(/(.)(.)(.)(.)/, '\4')
=> "444"

You don't have any groupings in your expression so '\4' is equivalent to ''.

 

[Mike Stok]

key = "file"
attrib = "\\Applications\\4Dapp\\Chess\\"
command = "xcopy [file] /y /s /e i:\\source\\"
command.gsub!( /\[#{key}\]/ , "#{attrib}" )
puts command
=> "xcopy \\ApplicationsDapp\\Chess\\ /y /s /e i:\\source\\"

As others have said, '\4' in a gsub string is special. To get around
this you need yet another backslash in front of it, which of course
means two more backslashes between the double quotes:

attrib = "\\Applications\\\\4Dapp\\Chess\\"

You can safely double all backslashes in gsub strings, so you might just
want to make it special-processing-proof automatically with some
preparatory munging of your own:

attrib = "\\Applications\\4Dapp\\Chess\\".gsub(/\\/, '\\\\\\')

Just as a side note, if you're going to be making literal strings with
backslashes, single quotes cut down on the number of doublings required:

attrib = '\Applications\4Dapp\Chess\\'.gsub(/\\/, '\\\\\\')

also if your replacement includes \ then you might consider using the
block form of gsub or gsub! to do the replacement as it doesn't parse
the replacement string for you (but does have some overhead):

[mike@ratdog mike]$ irb

key = "file" => "file"
attrib = "\\Applications\\4Dapp\\Chess\\" => "\\Applications\\4Dapp\\Chess\\"
command = "xcopy [file] /y /s /e i:\\source\\" => "xcopy [file] /y /s /e i:\\source\\"
command.gsub!(/\[#{key}\]/) { attrib } => "xcopy \\Applications\\4Dapp\\Chess\\ /y /s /e i:\\source\\"
puts command

xcopy \Applications\4Dapp\Chess\ /y /s /e i:\source\
=> nil

Hope this helps,

Mike