CODEWITHSUNDEEP
regexgrep
Ric
Ric

Reputation: 498

regex for first instance of a specific character that DOESN'T come immediately after another specific character

I have a function, translate(), takes multiple parameters. The first param is the only required and is a string, that I always wrap in single quotes, like this:

translate('hello world');

The other params are optional, but could be included like this:

translate('hello world', true, 1, 'foobar', 'etc');

And the string itself could contain escaped single quotes, like this:

translate('hello\'s world');

To the point, I now want to search through all code files for all instances of this function call, and extract just the string. To do so I've come up with the following grep, which returns everything between translate(' and either ') or ',. Almost perfect:

grep -RoPh "(?<=translate\(').*?(?='\)|'\,)" .

The problem with this though, is that if the call is something like this:

translate('hello \'world\', you\'re great!');

My grep would only return this:

hello \'world\

So I'm looking to modify this so that the part that currently looks for ') or ', instead looks for the first occurrence of ' that hasn't been escaped, i.e. doesn't immediately follow a \

Hopefully I'm making sense. Any suggestions please?

Upvotes: 1

Views: 208

Answers (2)

anubhava
anubhava

Reputation: 785721

You can use this grep with PCRE regex:

grep -RoPh "\btranslate\(\s*\K'(?:[^'\\\\]*)(?:\\\\.[^'\\\\]*)*'" .

Here is a regex demo

RegEx Breakup:

\b            # word boundary
translate     # match literal translate
\(            # match a (
\s*           # match 0 or more whitespace
\K            # reset the matched information
'             # match starting single quote
(?:           # start non-capturing group
   [^'\\\\]*  # match 0 or more chars that are not a backslash or single quote
)             # end non-capturing group
(?:           # start non-capturing group
   \\\\.      # match a backslash followed by char that is "escaped"
   [^'\\\\]*  # match 0 or more chars that are not a backslash or single quote
)*            # end non-capturing group
'             # match ending single quote

Here is a version without \K using look-arounds:

grep -oPhR "(?<=\btranslate\(')(?:[^'\\\\]*)(?:\\\\.[^'\\\\]*)*(?=')" .

RegEx Demo 2

Upvotes: 2

arensb
arensb

Reputation: 159

I think the problem is the .*? part: the ? makes it a non-greedy pattern, meaning it'll take the shortest string that matches the pattern. In effect, you're saying, "give me the shortest string that's followed by quote+close-paren or quote+comma". In your example, "world\" is followed by a single quote and a comma, so it matches your pattern. In these cases, I like to use something like the following reasoning:

A string is a quote, zero or more characters, and a quote: '.*'

A character is anything that isn't a quote (because a quote terminates the string): '[^']*'

Except that you can put a quote in a string by escaping it with a backslash, so a character is either "backslash followed by a quote" or, failing that, "not a quote": '(\\'|[^'])*'

Put it all together and you get

grep -RoPh "(?<=translate\(')(\\'|[^'])*(?='\)|'\,)" .

Upvotes: 0

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