Problem with gsub! in file


#1

I am new to Ruby and trying to do a find and replace on a text file
based on a regular expression. When I step through the code line by
line, it appears that the appropriate line in the file is changed, but
when I exit the function, the file hasn’t been modified. Are in-place
edits of files allowed? can you see what it wrong here?

Here is the body of the function:

def ReplaceGuid(guid)
r = nil
sconfProj = File.open(“myfile.vcproj”, “r+”).each do |line|
m = @guidExp.match(line)
if !m.nil?
str = m[1]
r = %r{#{str}}
line.gsub!(r, guid)
break
end
end
end

Many thanks,
Jen


#2

OK, I see now it’s not trivial to read and write from a file at the
same time, and instead I should probably just drop to the command line
and call
ruby -pe 'gsub(/foo/, "bar")' < myfile.vcproj

When i do this, the text of the file spits out to stdio, and it
appears the substitution has been made, but when I open the file in a
text editor, it hasn’t been changed.
Am I missing something?
I already checked file permissions and everything looks fine

Thanks,
Jen

`


#3

JenC wrote:

OK, I see now it’s not trivial to read and write from a file at the
same time, and instead I should probably just drop to the command line
and call
ruby -pe 'gsub(/foo/, "bar")' < myfile.vcproj

When i do this, the text of the file spits out to stdio, and it
appears the substitution has been made, but when I open the file in a
text editor, it hasn’t been changed.
Am I missing something?
I already checked file permissions and everything looks fine

Thanks,
Jen

`

You’ll want ruby -pie ‘gsub(/foo/,“bar”)’ myfile.vcproj

Or, if you want to keep a backup of the original (and you probably do,
until you know this works the way you expect), you can add an extension
of your choice to the -i flag:

ruby -p -i.bak e ‘gsub(/foo/,“bar”)’ myfile.vcproj

I’ve actually never used this on Windows, you’ll have to try it and see.


#4

Adam G. wrote:

ruby -p -i.bak e ‘gsub(/foo/,“bar”)’ myfile.vcproj

Er, sorry, make that ruby -p -i.bak -e ‘gsub(/foo/,“bar”)’
myfile.vcproj


#5

Thanks Adam. I tried this:
ruby -p -i.bak -e ‘gsub(/foo/,“bar”)’ myfile.vcproj

but them I get a whole load of warnings:
-e:1: warning: Can’t do inplace edit for stdio

and the file still doesn’t change… any ideas?

best,
Jen


#6

JenC wrote:

Thanks Adam. I tried this:
ruby -p -i.bak -e ‘gsub(/foo/,“bar”)’ myfile.vcproj

but them I get a whole load of warnings:
-e:1: warning: Can’t do inplace edit for stdio

and the file still doesn’t change… any ideas?

best,
Jen

Are you sure you did just ‘myfile.vcproj’ and not ‘< myfile.vcproj’?


#7
    sconfProj = File.open("myfile.vcproj", "r+").each do |line|

Many thanks,
Jen

The problem is this: you’re reading the contents of your file into
memory, changing the copy in memory and expecting it to propagate to the
physical file. Try this: (though I haven’t tested or run it, so there
might be some errors)

def ReplaceGuid(guid)
outfile = File.new(“Some_filename”, ‘w’)
found_match = false
IO.read(“myfile.vcproj”).each_line do |line|
if (@guidExp =~ (line)) && !found_match
line.gsub!($1, guid)
found_match = true
end
outfile.puts line
end
outfile.close
end

That reads in the original and writes the output to a new file. I’m
assuming you wanted to stop at the first match, which is what would
happen in your original code.

HTH,
Michael

=======================================================================
This email, including any attachments, is only for the intended
addressee. It is subject to copyright, is confidential and may be
the subject of legal or other privilege, none of which is waived or
lost by reason of this transmission.
If the receiver is not the intended addressee, please accept our
apologies, notify us by return, delete all copies and perform no
other act on the email.
Unfortunately, we cannot warrant that the email has not been
altered or corrupted during transmission.


#8

Are you sure you did just ‘myfile.vcproj’ and not ‘< myfile.vcproj’?
aha! that was it!

Thanks so much!

On Mar 24, 5:46 pm, Adam G. removed_email_address@domain.invalid wrote:

Jen