I'm trying to do something like the following. Let's say i have the following string:
"some string"
And i wanted to replace the space with a \1. However, wether i use single or double quote, i dont get the result:
"some string".gsub(" ", "\1") => "somestring"
"some string".gsub(" ", '\1') => "somestring"
"some string".gsub(" ", '\\1') => "somestring"
What i want is:
"some\1string"
Any suggestions?
This is only annoying because \1 through \9 are reserved for use in substitutions.
A possible solution is:
"some string".gsub(" ", '\\\\1')
It's kind of ugly, but it works.
An alternative is to use the block style where substitution isn't performed:
"some string".gsub(" ") { '\1' }
Remember that the output will be "some\\1string" because backslash is represented as \\ inside a double-quoted string. If you print it out you will get a single backslash.
This is also possible:
s = "some string"
p s.split.join('\1') # "some\\1string"
Related
s = "#main= 'quotes'
s.gsub "'", "\\'" # => "#main= quotes'quotes"
This seems to be wrong, I expect to get "#main= \\'quotes\\'"
when I don't use escape char, then it works as expected.
s.gsub "'", "*" # => "#main= *quotes*"
So there must be something to do with escaping.
Using ruby 1.9.2p290
I need to replace single quotes with back-slash and a quote.
Even more inconsistencies:
"\\'".length # => 2
"\\*".length # => 2
# As expected
"'".gsub("'", "\\*").length # => 2
"'a'".gsub("'", "\\*") # => "\\*a\\*" (length==5)
# WTF next:
"'".gsub("'", "\\'").length # => 0
# Doubling the content?
"'a'".gsub("'", "\\'") # => "a'a" (length==3)
What is going on here?
You're getting tripped up by the specialness of \' inside a regular expression replacement string:
\0, \1, \2, ... \9, \&, \`, \', \+
Substitutes the value matched by the nth grouped subexpression, or by the entire match, pre- or postmatch, or the highest group.
So when you say "\\'", the double \\ becomes just a single backslash and the result is \' but that means "The string to the right of the last successful match." If you want to replace single quotes with escaped single quotes, you need to escape more to get past the specialness of \':
s.gsub("'", "\\\\'")
Or avoid the toothpicks and use the block form:
s.gsub("'") { |m| '\\' + m }
You would run into similar issues if you were trying to escape backticks, a plus sign, or even a single digit.
The overall lesson here is to prefer the block form of gsub for anything but the most trivial of substitutions.
s = "#main = 'quotes'
s.gsub "'", "\\\\'"
Since \it's \\equivalent if you want to get a double backslash you have to put four of ones.
You need to escape the \ as well:
s.gsub "'", "\\\\'"
Outputs
"#main= \\'quotes\\'"
A good explanation found on an outside forum:
The key point to understand IMHO is that a backslash is special in
replacement strings. So, whenever one wants to have a literal
backslash in a replacement string one needs to escape it and hence
have [two] backslashes. Coincidentally a backslash is also special in a
string (even in a single quoted string). So you need two levels of
escaping, makes 2 * 2 = 4 backslashes on the screen for one literal
replacement backslash.
source
s = "#main= 'quotes'
s.gsub "'", "\\'" # => "#main= quotes'quotes"
This seems to be wrong, I expect to get "#main= \\'quotes\\'"
when I don't use escape char, then it works as expected.
s.gsub "'", "*" # => "#main= *quotes*"
So there must be something to do with escaping.
Using ruby 1.9.2p290
I need to replace single quotes with back-slash and a quote.
Even more inconsistencies:
"\\'".length # => 2
"\\*".length # => 2
# As expected
"'".gsub("'", "\\*").length # => 2
"'a'".gsub("'", "\\*") # => "\\*a\\*" (length==5)
# WTF next:
"'".gsub("'", "\\'").length # => 0
# Doubling the content?
"'a'".gsub("'", "\\'") # => "a'a" (length==3)
What is going on here?
You're getting tripped up by the specialness of \' inside a regular expression replacement string:
\0, \1, \2, ... \9, \&, \`, \', \+
Substitutes the value matched by the nth grouped subexpression, or by the entire match, pre- or postmatch, or the highest group.
So when you say "\\'", the double \\ becomes just a single backslash and the result is \' but that means "The string to the right of the last successful match." If you want to replace single quotes with escaped single quotes, you need to escape more to get past the specialness of \':
s.gsub("'", "\\\\'")
Or avoid the toothpicks and use the block form:
s.gsub("'") { |m| '\\' + m }
You would run into similar issues if you were trying to escape backticks, a plus sign, or even a single digit.
The overall lesson here is to prefer the block form of gsub for anything but the most trivial of substitutions.
s = "#main = 'quotes'
s.gsub "'", "\\\\'"
Since \it's \\equivalent if you want to get a double backslash you have to put four of ones.
You need to escape the \ as well:
s.gsub "'", "\\\\'"
Outputs
"#main= \\'quotes\\'"
A good explanation found on an outside forum:
The key point to understand IMHO is that a backslash is special in
replacement strings. So, whenever one wants to have a literal
backslash in a replacement string one needs to escape it and hence
have [two] backslashes. Coincidentally a backslash is also special in a
string (even in a single quoted string). So you need two levels of
escaping, makes 2 * 2 = 4 backslashes on the screen for one literal
replacement backslash.
source
So I'm having an issue replacing \" in a string.
My Objective:
Given a string, if there's an escaped quote in the string, replace it with just a quote
So for example:
"hello\"74" would be "hello"74"
simp"\"sons would be simp"sons
jump98" would be jump98"
I'm currently trying this: but obviously that doesn't work and messes everything up, any assistance would be awesome
str.replace "\\"", "\""
I guess you are being mistaken by how \ works. You can never define a string as
a = "hello"74"
Also escape character is used only while defining the variable its not part of the value. Eg:
a = "hello\"74"
# => "hello\"74"
puts a
# hello"74
However in-case my above assumption is incorrect following example should help you:
a = 'hello\"74'
# => "hello\\\"74"
puts a
# hello\"74
a.gsub!("\\","")
# => "hello\"74"
puts a
# hello"74
EDIT
The above gsub will replace all instances of \ however OP needs only to replace '" with ". Following should do the trick:
a.gsub!("\\\"","\"")
# => "hello\"74"
puts a
# hello"74
You can use gsub:
word = 'simp"\"sons';
print word.gsub(/\\"/, '"');
//=> simp""sons
I'm currently trying str.replace "\\"", "\"" but obviously that doesn't work and messes everything up, any assistance would be awesome
str.replace "\\"", "\"" doesn't work for two reasons:
It's the wrong method. String#replace replaces the entire string, you are looking for String#gsub.
"\\"" is incorrect: " starts the string, \\ is a backslash (correctly escaped) and " ends the string. The last " starts a new string.
You have to either escape the double quote:
puts "\\\"" #=> \"
Or use single quotes:
puts '\\"' #=> \"
Example:
content = <<-EOF
"hello\"74"
simp"\"sons
jump98"
EOF
puts content.gsub('\\"', '"')
Output:
"hello"74"
simp""sons
jump98"
I want to replace $word with another word in the following string:
"Hello $word How are you"
I used /\$(.*)/, /\$(.*)(\s)/ , /\$(.* \s)/. Due to *, I get the whole string after $, but I only need that word; I need to escape the space. I tried /s,\b, and few other options, but I cannot figure it out. Any help would be appreciated.
* is a greedy operator meaning it will match as much as it can and still allow the remainder of the regular expression to match. The token .* will greedily match every single character in the string. The regex engine will then advance to the next token \s which matches the last whitespace before the word "you" in the string given you a result of word How are.
You can use \S in place of .* which matches any non-whitespace characters.
\$\S+
Or to simply match only word characters, you can use the following:
\$\w+
If you only want to replace "$world" using a regex, try this:
"Hello $word How are you".gsub(/\$word/, 'other_word')
Or:
"Hello $word How are you".sub('$word',"*")
You can read more for gsub here: http://www.ruby-doc.org/core-2.2.0/String.html#method-i-gsub
Substituting placeholder words for other words is usually not done with a regex but with the % method and a hash:
h = {word: "aaa", other_word: "bbb"}
p "Hello %{word} How are you. %{other_word}. Bye %{word}" % h
# => "Hello aaa How are you. bbb. Bye aaa"
Consider:
>> string = "Hello $word How are you"
=> "Hello $word How are you"
>> replace_regex = /(?<replace_word>\$\w+)/
=> /(?<replace_word>\$\w+)/
>> string.gsub(replace_regex, "Bob")
=> "Hello Bob How are you"
>> string.match(replace_regex)[:replace_word]
=> "$word"
Note:
replace_word is the regex with a named capture group.
I want to insert backslash before apostrophe in "children's world" string. Is there a easy way to do it?
irb(main):035:0> s = "children's world"
=> "children's world"
irb(main):036:0> s.gsub('\'', '\\\'')
=> "childrens worlds world"
Answer
You need some extra backslashes:
>> puts "children's world".gsub("'", '\\\\\'')
children\'s world
or slightly more concisely (since you don't need to escape the ' in a double-quoted string):
>> puts "children's world".gsub("'", "\\\\'")
children\'s world
or even more concisely:
>> puts "children's world".gsub("'") { "\\'" }
children\'s world
Explanation
Your '\\\'' generates \' as a string:
>> puts '\\\''
\'
and \' is a special replacement pattern in Ruby. From ruby-doc.org:
you may refer to some special match variables using these combinations ... \' corresponds to $', which contains string after match
So the \' that gsub sees in the second argument is being interpreted as a special pattern (everything in the original string after the match) instead of as a literal \'.
So what you want gsub to see is actually \\', which can be produced by '\\\\\'' or "\\\\'".
Or, if you use the block form of gsub (gsub("xxx") { "yyy" }) then Ruby takes the replacement string "yyy" literally without trying to apply replacement patterns.
Note: If you have to create a replacement string with a lot of \s you could take advantage of the fact that when you use /.../ (or %r{...}) you don't have to double-escape the backslashes:
>> puts "children's world".gsub("'", /\\'/.source)
children\'s world
Or you could use a single-quoted heredoc: (using <<'STR' instead of just <<STR)
>> puts "children's world".gsub("'", <<'STR'.strip)
\\'
STR
children\'s world
>> puts s.gsub("'", "\\\\'")
children\'s world
Your problem is that the string "\'" is meaningful to gsub in a replacement string. In order to make it work the way you want, you have to use the block form.
s.gsub("'") {"\\'"}