if /hello/ =~line

[Peter Loftus]

Got help with this code earlier its just checking a file for a line

Im really new to ruby ive used java and C before

just wondering what do i put in if i want to use a variable that is
holding the string eg VAR1 = "hello"

File.foreach "file.txt" do |line|
if /hello/ =~ line
puts "found it"
break
end
end

 

[Jeremy McAnally]

You can use string interpolation like you can with double quoted strings.

var1 = "hello"

File.foreach "file.txt" do |line|
if /#{var1}/ =~ line
puts "found it"
break
end
end

--Jeremy

Got help with this code earlier its just checking a file for a line

Im really new to ruby ive used java and C before

just wondering what do i put in if i want to use a variable that is
holding the string eg VAR1 = "hello"

File.foreach "file.txt" do |line|
if /hello/ =~ line
puts "found it"
break
end
end

--
http://www.jeremymcanally.com/

My books:
Ruby in Practice
http://www.manning.com/mcanally/

My free Ruby e-book
http://www.humblelittlerubybook.com/

My blogs:
http://www.mrneighborly.com/
http://www.rubyinpractice.com/

 

[Lee Jarvis]

Got help with this code earlier its just checking a file for a line

Im really new to ruby ive used java and C before

just wondering what do i put in if i want to use a variable that is
holding the string eg VAR1 = "hello"

File.foreach "file.txt" do |line|
if /hello/ =~ line
puts "found it"
break
end
end

var = "hello"
File.foreach "file.txt" do |line|
if /#{var}/ =~ line
puts "found it"
break
end
end

Perhaps?

Regards,
Lee

 

[Peter Loftus]

if /#{var1}/ =~ line

when i enter # thats just comments out the whole line
any reason for using #

 

[Jari Williamsson]

if /#{var1}/ =~ line

when i enter # thats just comments out the whole line
any reason for using #

# is not a comment inside a regexp or string


Best regards,

Jari Williamsson

 

[Jeremy McAnally]

Though your IDE may think you're commenting out the whole line, you're
not. It's the proper way to do string interpolation.

See here: http://www.zenspider.com/Languages/Ruby/QuickRef.html#6

Or, optionally, the Pickaxe book section on strings.

--Jeremy

if /#{var1}/ =~ line

when i enter # thats just comments out the whole line
any reason for using #

--
http://www.jeremymcanally.com/

My books:
Ruby in Practice
http://www.manning.com/mcanally/

My free Ruby e-book
http://www.humblelittlerubybook.com/

My blogs:
http://www.mrneighborly.com/
http://www.rubyinpractice.com/

 

[Jano Svitok]

Sometimes it's better to cache the /#{var}/ as in this case, new
regexp object is created on each pass through the cycle.
That might hurt the performance a bit. So:

var = "hello" + var_re = /#{var}/
File.foreach "file.txt" do |line|

- if /#{var}/ =~ line
+ if var_re =~ line

puts "found it"
break
end
end

(This might apply for 1.8 MRI only, other interpreters might be
different): When the regex literal contains #{}, the object
is created on each pass through the code. In the other case it's
created only once.

Jano

 

[Peter Loftus]

Thanks for explaining it

Cheers
Loftz

Though your IDE may think you're commenting out the whole line, you're
not. It's the proper way to do string interpolation.

See here: http://www.zenspider.com/Languages/Ruby/QuickRef.html#6

Or, optionally, the Pickaxe book section on strings.

--Jeremy


--
http://www.jeremymcanally.com/

My books:
Ruby in Practice
http://www.manning.com/mcanally/

My free Ruby e-book
http://www.humblelittlerubybook.com/

My blogs:
http://www.mrneighborly.com/
http://www.rubyinpractice.com/

 

[Lee Jarvis]

(This might apply for 1.8 MRI only, other interpreters might be
different): When the regex literal contains #{}, the object
is created on each pass through the code. In the other case it's
created only once.

True, you could use the Regexp class also then..

var = 'hello'
revar = Regexp.new(var)

if revar =~ line
#..
end

or perhaps

var = 'hello'
File.foreach 'file.txt' do |line|
if Regexp.new(var) =~ line
puts 'found it'
break
end
end

If you don't care how many times its created and you don't want to use
the '#' in your regexp matches because your IDE doesn't know any better.

Regards,
Lee

 

[yermej]

Sometimes it's better to cache the /#{var}/ as in this case, new
regexp object is created on each pass through the cycle.
That might hurt the performance a bit. So:


- if /#{var}/ =~ line
+ if var_re =~ line


(This might apply for 1.8 MRI only, other interpreters might be
different): When the regex literal contains #{}, the object
is created on each pass through the code. In the other case it's
created only once.

Jano

You can also use the /o option, which tells Ruby to compile the Regex
only once:

var = "hello"
File.foreach "file.txt" do |line|
if /#{var}/o =~ line
puts "found it"
break
end
end

 

[Jano Svitok]

You can also use the /o option, which tells Ruby to compile the Regex
only once:

var = "hello"
File.foreach "file.txt" do |line|
if /#{var}/o =~ line

puts "found it"
break
end
end

Thanks, I didn't know that... Now I see it even in the first pickaxe
book... I guess I should read it once more ;-)

 

[Martin DeMello]

True, you could use the Regexp class also then..

var = 'hello'
revar = Regexp.new(var)

# And don't miss the very useful Regexp.quote, which makes sure
everything in var is matched literally

revar = Regexp.new(Regexp.quote(var))

martin