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Hi All,

I dont know how to use a variable in a regex searchstring.
ruby seems to only handle hardcoded serachstring in
regex's. How do you do this. My code is below.

Also - how do you put a variable name in a
File.open("filename.txt") statement like this:
File.open(filevariable) where filevariable can
be set to anything? I could not find this in
the docs.

Thanks, --Joe
================ snip code ===============
#!/usr/bin/ruby

F = "filename.txt"
searchstring = ARGV[0]

print "searchstring is ", searchstring, "\n"


File.open("filename.txt").each { |line|
# this fails puts line if line =~ searchstring
# this fails puts line if line =~ /searchstring/
# this fails puts line if line =~ "searchstring"

#this works
# puts line
}

>
> I dont know how to use a variable in a regex searchstring.
> ruby seems to only handle hardcoded serachstring in
> regex's. =A0 How do you do this. =A0 My code is below.
>

Does this help?

str =3D "abcdef"
searchstring =3D "cd"
p str =3D~ /#{searchstring}/


Harry

On Jan 29, 10:38=A0pm, Harry Kakueki <list.p...@gmail.com> wrote:
> > I dont know how to use a variable in a regex searchstring.
> > ruby seems to only handle hardcoded serachstring in
> > regex's. =A0 How do you do this. =A0 My code is below.
>
> Does this help?
>
> str =3D "abcdef"
> searchstring =3D "cd"
> p str =3D~ /#{searchstring}/

You may need to escape:

p str =3D~ /#{Regexp.escape(searchstring)}/

Thomas Sawyer wrote:
> On Jan 29, 10:38�pm, Harry Kakueki <list.p...@gmail.com> wrote:
>> > I dont know how to use a variable in a regex searchstring.
>> > ruby seems to only handle hardcoded serachstring in
>> > regex's. � How do you do this. � My code is below.
>>
>> Does this help?
>>
>> str = "abcdef"
>> searchstring = "cd"
>> p str =~ /#{searchstring}/
>
> You may need to escape:
>
> p str =~ /#{Regexp.escape(searchstring)}/

But note that #{} only makes sense if you're interpolating a variable
into part of a regex -- say, /January #{year}/. If the variable is the
whole regex, then it's more sensible to do Regex.new(searchstring).


Best,
--
Marnen Laibow-Koser
http://www.marnen.org

--
Posted via http://www.ruby-forum.com/.

[Note: parts of this message were removed to make it a legal post.]

On Fri, Jan 29, 2010 at 6:50 PM, joemac <> wrote:

> Hi All,
>
> I dont know how to use a variable in a regex searchstring.
> ruby seems to only handle hardcoded serachstring in
> regex's. How do you do this. My code is below.
>
> Also - how do you put a variable name in a
> File.open("filename.txt") statement like this:
> File.open(filevariable) where filevariable can
> be set to anything? I could not find this in
> the docs.
>
> Thanks, --Joe
> ================ snip code ===============
> #!/usr/bin/ruby
>
> F = "filename.txt"
> searchstring = ARGV[0]
>
> print "searchstring is ", searchstring, "\n"
>
>
> File.open("filename.txt").each { |line|
> # this fails puts line if line =~ searchstring
> # this fails puts line if line =~ /searchstring/
> # this fails puts line if line =~ "searchstring"
>
> #this works
> # puts line
> }
>
>
This should work, here is an image showing how to use it:
http://tinypic.com/r/b5pi7m/6

filename = 'source.txt'
to_find = Regexp.new ARGV[0]

puts "The Regexp is: #{to_find.inspect}"

File.open(filename).each do |line|
if line =~ to_find
puts "This line matches: #{line}"
puts "This is what matches: #{line[to_find]}"
end
end

Josh Cheek wrote:
> File.open(filename).each do |line|
> if line =~ to_find
> puts "This line matches: #{line}"
> puts "This is what matches: #{line[to_find]}"

or to avoid having to match it twice:

puts "This is what matches: #{$&}"

Also:
puts "This is what came before: #{$`}"
puts "This is what came after: #{$'}"
puts "Capture 1 is #{$1}"
# etc
--
Posted via http://www.ruby-forum.com/.

On Jan 29, 7:38*pm, Harry Kakueki <list.p...@gmail.com> wrote:
> > I dont know how to use avariablein a regex searchstring.
> > ruby seems to only handle hardcoded serachstring in
> > regex's. * How do you do this. * My code is below.
>
> Does this help?
>
> str = "abcdef"
> searchstring = "cd"
> p str =~ /#{searchstring}/
>
> Harry

Hi Folks,

Thanks for all the helpful info.
It was the #{} syntax that i was missing.
This also works for the "filename as a varible" situation
when parsing lots of files:

filenames = ["input1", "input2", "input3"]

for fname in filenames
infile = File.open("#{fname}")
while line = infile.gets()
puts line
end
puts "================== end file ==================="
end


Very helpfull!

Thanks, --JM

On Feb 22, 2010, at 1:45 PM, joemac wrote:
> On Jan 29, 7:38 pm, Harry Kakueki <list.p...@gmail.com> wrote:
>>> I dont know how to use avariablein a regex searchstring.
>>> ruby seems to only handle hardcoded serachstring in
>>> regex's. How do you do this. My code is below.
>>
>> Does this help?
>>
>> str = "abcdef"
>> searchstring = "cd"
>> p str =~ /#{searchstring}/
>>
>> Harry
>
> Hi Folks,
>
> Thanks for all the helpful info.
> It was the #{} syntax that i was missing.
> This also works for the "filename as a varible" situation
> when parsing lots of files:
>
> filenames = ["input1", "input2", "input3"]
>
> for fname in filenames
> infile = File.open("#{fname}")
> while line = infile.gets()
> puts line
> end
> puts "================== end file ==================="
> end
>
>
> Very helpfull!
>
> Thanks, --JM

In this case, you're already getting strings in fname so "#{fname}"
isn't really doing anything useful.

-Rob

Rob Biedenharn http://agileconsultingllc.com

> In this case, you're already getting strings in fname so "#{fname}" isn't
> really doing anything useful.

Which means File.open(fname) would work directly.

Cheers,

--=20
JJ Fleck
PCSI1 Lyc=E9e Kl=E9ber