How do I include a variable in the 'replace' portion of gsub?
replace.gsub(/#{year}","1/, '#{year}","b')
This outputs:
=> #{year}","b
Let's say year = 2013. I want it to output:
=> 2013","b
Adding on to Blender's answer, you can use an alternate way of writing strings to avoid having to escape quotes:
replace.gsub(/#{year}","1/, %{#{year}","b})
where %{} is another way to write a string literal that you can do string interpolation in.
Related
I'm new to ruby and Chef and am running to an issue with syntax when defining attributes in my cookbook. Below is relevant code:
default[:my_cookbook][:stuff] = {
:foo_bar => {
:grok => ['Hi'],
:2grok => ['Bye'],
...
It appears I can't use a number to begin 2grok.. Is there a way to escape this, or what would be the proper syntax to use '2grok'?
If you want to start a symbol with a digit, you need to enclose it in quotes:
:'2grok' => ['Hi']
If you use double quotes, ruby interpolates string inside:
:"#{1 + 1}grok"
Also, you can use percent-notation:
%s{2grok}
Finally, you can get the symbol by calling to_sym method on a String:
'2grok'.to_sym => ['Hi']
Mladen's answer is correct in term of Ruby. You can use a number at the beginning of symbol's name only using quotes. Keep in mind that you will have to use them to access the value from hash too. However you shouldn't use symbols for defining attributes in your cookbooks. Chef Style Guide recommends using strings instead.
I often see the gsub function being called with the pattern parameter enclosed in forward slashes. For example:
>> phrase = "*** and *** ran to the ###."
>> phrase.gsub(/\*\*\*/, "WOOF")
=> "WOOF and WOOF ran to the ###."
I thought maybe it had something to do with escaping asterisks, but using single quotes and double quotes works just as well:
>> phrase = "*** and *** ran to the ###."
>> phrase.gsub('***', "WOOF")
=> "WOOF and WOOF ran to the ###."
>> phrase.gsub("***", "WOOF")
=> "WOOF and WOOF ran to the ###."
Is it just convention to use forward slash? What am I missing?
Use forward slashes if you need to use regular expressions.
If you use a string argument with gsub, it will just do a plain character match.
In your example, you need backslashes to escape the asterisks when using a regular expression, because asterisks have a special meaning in regex (optionally match something any number of times). They are not necessary when using a string, because they are just matched exactly.
In your example, you probably don't need to use a regular expression, since it is a simple pattern. However, if you wanted to match *** only when it was at the beginning of a string (e.g. the first bunch in your example), then you would want to use a regex, for example:
phrase.gsub(/^\*{3}/, "WOOF")
For more information on regular expressions, see: http://www.regular-expressions.info/.
For more information on using regular expressions in Ruby, see: http://ruby-doc.org/core-2.2.0/Regexp.html.
To play with regular expressions as they work in Ruby, try: http://rubular.com/.
You are missing reading the documentation:
The pattern is typically a Regexp; if given as a String, any regular expression metacharacters it contains will be interpreted literally, e.g. '\d' will match a backlash followed by ‘d’, instead of a digit.
http://ruby-doc.org/core-2.1.4/String.html#method-i-gsub
In other words, you can give a string or a regular expression. Regular expressions can be delimited several ways:
Regexps are created using the /.../ and %r{...} literals, and by the Regexp::new constructor.
http://ruby-doc.org/core-2.2.2/Regexp.html
The benefit of %r and of the alternate %r delimiters is you can usually find a delimiter that doesn't collide with characters in the pattern, which would force escaping them, as in your example.
* has to be escaped because it has special meaning in a regex, but in a string it does not.
Why does this string not split on each "\n"? (RUBY)
"ADVERTISING [7310]\n\t\tIRS NUMBER:\t\t\t\t061340408\n\t\tSTATE OF INCORPORATION:\t\t\tDE\n\t\tFISCAL YEAR END:\t\t\t0331\n\n\tFILING VALUES:\n\t\tFORM TYPE:\t\t10-Q\n\t\tSEC ACT:\t\t1934 Act\n\t".split('\n')
>> ["ADVERTISING [7310]\n\t\tIRS NUMBER:\t\t\t\t061340408\n\t\tSTATE OF INCORPORATION:\t\t\tDE\n\t\tFISCAL YEAR END:\t\t\t0331\n\n\tFILING VALUES:\n\t\tFORM TYPE:\t\t10-Q\n\t\tSEC ACT:\t\t1934 Act\n\t"]
You need .split("\n"). String interpolation is needed to properly interpret the new line, and double quotes are one way to do that.
In Ruby single quotes around a string means that escape characters are not interpreted. Unlike in C, where single quotes denote a single character. In this case '\n' is actually equivalent to "\\n".
So if you want to split on \n you need to change your code to use double quotes.
.split("\n")
Ruby has the methods String#each_line and String#lines
returns an enum:
http://www.ruby-doc.org/core-1.9.3/String.html#method-i-each_line
returns an array:
http://www.ruby-doc.org/core-2.1.2/String.html#method-i-lines
I didn't test it against your scenario but I bet it will work better than manually choosing the newline chars.
Or a regular expression
.split(/\n/)
You can't use single quotes for this:
"ADVERTISING [7310]\n\t\tIRS NUMBER:\t\t\t\t061340408\n\t\tSTATE OF INCORPORATION:\t\t\tDE\n\t\tFISCAL YEAR END:\t\t\t0331\n\n\tFILING VALUES:\n\t\tFORM TYPE:\t\t10-Q\n\t\tSEC ACT:\t\t1934 Act\n\t".split("\n")
I am writing a script that deals with hex color values and I want to substitute in a user provided variable after a hash mark like so:
HEX=$1
COLOR='#$HEX'
But this fails as I believe it is interpreting the hash as a comment? How do I escape the hash so that I can have a variable which contains a string with a hash in it?
That fails because you're using single quotes. There's no variable substitution inside single quotes. Instead, use double quoted:
COLOR="#$HEX"
Single quotes block dollar interpolation. Double ones don't, so this should work:
COLOR="#$HEX"
Is there some way in Ruby that I can avoid having to put double-backslash in Ruby strings (like what can be done in C#):
For example, in C# was can prefix a string with # and then the backslash in the string does not need to be escaped:
#"C:\Windows, C:\ABC"
Without # we would need to escape the backslash:
"C:\\Windows, C:\\ABC"
Is there something similar in Ruby?
Use single quotes
my_string = 'C:\Windows'
See more in the Strings section here
You can also use %q and backslashes will be automatically escaped for you:
%q{C:\Windows} => "C:\\Windows"