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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 ./.)
26 lines
596 B
Nix
26 lines
596 B
Nix
with builtins;
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let
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matches = pat: s: match pat s != null;
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splitFN = match "((.*)/)?([^/]*)\\.(nix|cc)";
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in
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assert matches "foobar" "foobar";
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assert matches "fo*" "f";
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assert !matches "fo+" "f";
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assert matches "fo*" "fo";
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assert matches "fo*" "foo";
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assert matches "fo+" "foo";
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assert matches "fo{1,2}" "foo";
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assert !matches "fo{1,2}" "fooo";
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assert !matches "fo*" "foobar";
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assert match "(.*)\\.nix" "foobar.nix" == [ "foobar" ];
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assert splitFN "/path/to/foobar.nix" == [ "/path/to/" "/path/to" "foobar" "nix" ];
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assert splitFN "foobar.cc" == [ null null "foobar" "cc" ];
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true
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