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The function ‘builtins.match’ takes a POSIX extended regular
expression and an arbitrary string. It returns ‘null’ if the string
does not match the regular expression. Otherwise, it returns a list
containing substring matches corresponding to parenthesis groups in
the regex. The regex must match the entire string (i.e. there is an
implied "^<pat>$" around the regex). For example:
match "foo" "foobar" => null
match "foo" "foo" => []
match "f(o+)(.*)" "foooobar" => ["oooo" "bar"]
match "(.*/)?([^/]*)" "/dir/file.nix" => ["/dir/" "file.nix"]
match "(.*/)?([^/]*)" "file.nix" => [null "file.nix"]
The following example finds all regular files with extension .nix or
.patch underneath the current directory:
let
findFiles = pat: dir: concatLists (mapAttrsToList (name: type:
if type == "directory" then
findFiles pat (dir + "/" + name)
else if type == "regular" && match pat name != null then
[(dir + "/" + name)]
else []) (readDir dir));
in findFiles ".*\\.(nix|patch)" (toString ./.)
29 lines
453 B
C++
29 lines
453 B
C++
#pragma once
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#include "types.hh"
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#include <sys/types.h>
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#include <regex.h>
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#include <map>
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namespace nix {
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MakeError(RegexError, Error)
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class Regex
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{
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public:
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Regex(const string & pattern, bool subs = false);
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~Regex();
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bool matches(const string & s);
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typedef std::map<unsigned int, string> Subs;
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bool matches(const string & s, Subs & subs);
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private:
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unsigned nrParens;
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regex_t preg;
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string showError(int err);
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};
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}
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