[groovy-user] replacing backslashes per pattern in a string
Detering Dirk
what is the correct way to replace backslashes
in a string representing a DOS path with single slashes?
Trying to use path.replaceAll(/\/, "/") does not work.
(BTW: The error message is:
org.codehaus.groovy.control.MultipleCompilationErrorsException:
startup failed, PluginErrorCheck.groovy: 9: expecting anything but '
'\n''; got it anyway @ line 9, column 34.
println x.replaceAll(/\/, "/")
The column hints to different places after replaceAll depending
on the other code around this method call in the same line.)
Use double backslashes in the expression gives the same result.
The only solution I got to work is to use normal strings and
use four(!) backslashes in the regex:
println x.replaceAll("\\\\", "/")
Even the trick mentioned in GinA in the footnote on p. 70
does not work, it needs to be:
def regex = /${'\\\\'}/
When you only do:
def regex = /${'\\'}/
and call
println x.replaceAll(regex, "/")
you get:
Caught: java.util.regex.PatternSyntaxException:
Unexpected internal error near index 1
\
^
No way around that?
KR
Det
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Paul King
> Hello all,
>
> what is the correct way to replace backslashes
> in a string representing a DOS path with single slashes?
>
> Trying to use path.replaceAll(/\/, "/") does not work.
Yes, you can't have a backslash as the last character
of a slashy string because it is the escape character
for putting backslashes into the string. So what you
had was correct unless you want to not use regexs:
def x = /C:\Windows\Temp/
println x.replaceAll('\\\\', '/')
println new File(x).toURI().toString() - 'file:/'
Paul.
Detering Dirk
thanks Paul,
> > what is the correct way to replace backslashes in a string
> > representing a DOS path with single slashes?
> >
> > Trying to use path.replaceAll(/\/, "/") does not work.
>
> Yes, you can't have a backslash as the last character of a
> slashy string because it is the escape character for putting
> backslashes into the string.
The problem occured when peer-reviewing a committed source and
was slightly obscured as my question rendered my own tests.
Did a test today on another machine having groovy 1.0 installed
(like the original committer had), so the real problem was hidden
in a side note in my text:
> > Use double backslashes in the expression gives the same result.
So here is a test, checked in GroovyConsole:
Version 1.0:
groovy> x = "D:\\this\\is\\a\\file"
groovy> println x
groovy> r = x.replaceAll(/\\/, "/")
groovy> println r
D:\this\is\a\file
D:/this/is/a/file
Version 1.5.4:
groovy> x = "D:\\this\\is\\a\\file"
groovy> println x
groovy> r = x.replaceAll(/\\/, "/")
groovy> println r
Exception thrown:
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup
failed, Script1: 3: expecting anything but ''\n''; got it anyway @ line
3, column 28.
1 error
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup
failed, Script1: 3: expecting anything but ''\n''; got it anyway @ line
3, column 28.
1 error
Code breaking change with 1.5 or subject for a JIRA issue?
KR
Det
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Geschaeftsfuehrer: Gernot Kiefer
Paul King
This was changed in 1.5. The example above still has a backslash as
the last character of a slashy string which isn't allowed. In 1.0 you
weren't allowed to have an odd number of backslashes anywhere in the
slashy string.
Paul.
> KR
> Det
Detering Dirk
> > groovy> x = "D:\\this\\is\\a\\file"
> > groovy> println x
> > groovy> r = x.replaceAll(/\\/, "/")
> > groovy> println r
> >
> > D:\this\is\a\file
> > D:/this/is/a/file
[...]
> This was changed in 1.5. The example above still has a
> backslash as the last character of a slashy string which
> isn't allowed.
VERY annoying. The 1.5 behaviour is not groovy when scripting
a windose machine, where you often have to replace the
unfortunate backslash in pathes. Most typical application for
replace with pattern AFAIC.
The behaviour of 1.0 (same as Ruby's x.gsub(/\\/, "/") btw )
was a convenient, for every one intuitive way.
> In 1.0 you weren't allowed to have an odd
> number of backslashes anywhere in the slashy string.
Quite understandable. But there isn't an odd number in the
mentioned commited solution, which was coded like to be seen
above.
NB: Such changes make it hard to be a Groovy evangelist
in my company ... :-( .
The question came:
Do we have to factor out such simple things and unit test them?
Say: Do we have to unit test Groovy itsself to save our implementations?
Just my 2ct
KR
Det
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Geschaeftsfuehrer: Gernot Kiefer
Paul King
Well, there was a big debate on the mailing list and eventually
we decided to make the change. There were several broken things
about the old way of doing things.
You couldn't have strings like /C:\this\is\a\file/ because
it has 4 occurrences of an odd number of backslashes. You
also couldn't have slashes in slashy strings. What if my original
string had 1, 3, 5, 7, ... backslashes. There would be no way to
get rid of those. You couldn't have .replaceAll(/\\\/, 'X') because
that has an odd number of backslashes.
In the end, we thought there were enough workarounds for cases
were you might have a backslash at the end of a slashy string:
x = /C:\this\is\a\file/
println x
// ----------------------
r = x.replaceAll(/\\${''}/, "/")
println r
// ----------------------
e = ''
r = x.replaceAll(/\\$e/, "/")
println r
// ----------------------
r = x.replaceAll('\\\\', "/")
println r
// ----------------------
r = new File(x).toURI().toString() - 'file:/'
println r
// ----------------------
r = x.tokenize('\\').join('/')
println r
// ----------------------
String.metaClass.gsub = { from, to ->
delegate.tokenize(from).join(to)
}
r = x.gsub('\\', '/')
println r
// ----------------------
It isn't perfect but it was the best that the mailing list
could come up with at the time.
Paul.
> The question came:
> Do we have to factor out such simple things and unit test them?
> Say: Do we have to unit test Groovy itsself to save our implementations?
>
> Just my 2ct
> KR
> Det
Detering Dirk
thank you for your explanation and the list of workarounds.
I indeed like this for its similar expressiveness:
> r = x.tokenize('\\').join('/')
[...]
> r = x.gsub('\\', '/')
Well, this gsub thing as part of the GDK String extension
seems attractive ... too useful for a handmade metaclass
enhancement.
(What shall I say now? Don't switch languages too often and
know the APIs better ;-) ).
KR
Det
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Geschaeftsfuehrer: Gernot Kiefer