Elixir v1.4.5 Regex View Source
Provides regular expressions for Elixir.
Regex is based on PCRE (Perl Compatible Regular Expressions) and
built on top of Erlang’s :re
module. More information can be found
in the :re
module documentation.
Regular expressions in Elixir can be created using the sigils
~r
or ~R
:
# A simple regular expressions that matches foo anywhere in the string
~r/foo/
# A regular expression with case insensitive and Unicode options
~r/foo/iu
Regular expressions created via sigils are pre-compiled and stored
in the .beam
file. Notice this may be a problem if you are precompiling
Elixir, see the “Precompilation” section for more information.
A Regex is represented internally as the Regex
struct. Therefore,
%Regex{}
can be used whenever there is a need to match on them.
Keep in mind it is not guaranteed two regular expressions from the same source are equal, for example:
~r/(?<foo>.)(?<bar>.)/ == ~r/(?<foo>.)(?<bar>.)/
may return true
or false
depending on your machine, endianess,
available optimizations and others. You can, however, retrieve the source
of a compiled regular expression by accessing the source
field, and then
compare those directly:
~r/(?<foo>.)(?<bar>.)/.source == ~r/(?<foo>.)(?<bar>.)/.source
Precompilation
Regular expressions built with sigil are precompiled and stored in .beam
files. This may be a problem if you are precompiling Elixir to run in
different OTP releases, as OTP releases may update the underlying regular
expression engine at any time.
For such reasons, we always recomend precompiling Elixir projects using
the OTP version meant to run in production. In case cross-compilation is
really necessary, you can manually invoke Regex.recompile/1
or Regex.
recompile!/1
to perform a runtime version check and recompile the regex
if necessary.
Modifiers
The modifiers available when creating a Regex are:
unicode
(u) - enables Unicode specific patterns like\p
and change modifiers like\w
,\W
,\s
and friends to also match on Unicode. It expects valid Unicode strings to be given on matchcaseless
(i) - adds case insensitivitydotall
(s) - causes dot to match newlines and also set newline to anycrlf; the new line setting can be overridden by setting(*CR)
or(*LF)
or(*CRLF)
or(*ANY)
according to re documentationmultiline
(m) - causes^
and$
to mark the beginning and end of each line; use\A
and\z
to match the end or beginning of the stringextended
(x) - whitespace characters are ignored except when escaped and allow#
to delimit commentsfirstline
(f) - forces the unanchored pattern to match before or at the first newline, though the matched text may continue over the newlineungreedy
(U) - inverts the “greediness” of the regexp (the previousr
option is deprecated in favor ofU
)
The options not available are:
anchored
- not available, use^
or\A
insteaddollar_endonly
- not available, use\z
insteadno_auto_capture
- not available, use?:
insteadnewline
- not available, use(*CR)
or(*LF)
or(*CRLF)
or(*ANYCRLF)
or(*ANY)
at the beginning of the regexp according to the re documentation
Captures
Many functions in this module handle what to capture in a regex
match via the :capture
option. The supported values are:
:all
- all captured subpatterns including the complete matching string (this is the default):first
- only the first captured subpattern, which is always the complete matching part of the string; all explicitly captured subpatterns are discarded:all_but_first
- all but the first matching subpattern, i.e. all explicitly captured subpatterns, but not the complete matching part of the string:none
- does not return matching subpatterns at all:all_names
- captures all names in the Regexlist(binary)
- a list of named captures to capture
Link to this section Summary
Functions
Compiles the regular expression
Compiles the regular expression and raises Regex.CompileError
in case of errors
Escapes a string to be literally matched in a regex
Returns a boolean indicating whether there was a match or not
Returns the given captures as a map or nil
if no captures are
found. The option :return
can be set to :index
to get indexes
back
Returns a list of names in the regex
Returns the regex options as a string
Returns the underlying re_pattern
in the regular expression
Recompiles the existing regular expression if necessary
Recompiles the existing regular expression and raises Regex.CompileError
in case of errors
Returns true
if the given term
is a regex.
Otherwise returns false
Receives a regex, a binary and a replacement, returns a new binary where all matches are replaced by the replacement
Runs the regular expression against the given string until the first match.
It returns a list with all captures or nil
if no match occurred
Same as run/3
, but scans the target several times collecting all
matches of the regular expression
Returns the regex source as a binary
Splits the given target based on the given pattern and in the given number of parts
Returns the version of the underlying Regex engine
Link to this section Types
t() :: %Regex{opts: binary, re_pattern: term, re_version: term, source: binary}
Link to this section Functions
compile(binary, binary | [term]) :: {:ok, t} | {:error, any}
Compiles the regular expression.
The given options can either be a binary with the characters
representing the same regex options given to the ~r
sigil,
or a list of options, as expected by the Erlang’s :re
module.
It returns {:ok, regex}
in case of success,
{:error, reason}
otherwise.
Examples
iex> Regex.compile("foo")
{:ok, ~r"foo"}
iex> Regex.compile("*foo")
{:error, {'nothing to repeat', 0}}
compile!(binary, binary | [term]) :: t
Compiles the regular expression and raises Regex.CompileError
in case of errors.
Escapes a string to be literally matched in a regex.
Examples
iex> Regex.escape(".")
"\\."
iex> Regex.escape("\\what if")
"\\\\what\\ if"
Returns a boolean indicating whether there was a match or not.
Examples
iex> Regex.match?(~r/foo/, "foo")
true
iex> Regex.match?(~r/foo/, "bar")
false
Returns the given captures as a map or nil
if no captures are
found. The option :return
can be set to :index
to get indexes
back.
Examples
iex> Regex.named_captures(~r/c(?<foo>d)/, "abcd")
%{"foo" => "d"}
iex> Regex.named_captures(~r/a(?<foo>b)c(?<bar>d)/, "abcd")
%{"bar" => "d", "foo" => "b"}
iex> Regex.named_captures(~r/a(?<foo>b)c(?<bar>d)/, "efgh")
nil
Returns the underlying re_pattern
in the regular expression.
Recompiles the existing regular expression if necessary.
This checks the version stored in the regular expression and recompiles the regex in case of version mismatch.
Recompiles the existing regular expression and raises Regex.CompileError
in case of errors.
Returns true
if the given term
is a regex.
Otherwise returns false
.
Examples
iex> Regex.regex?(~r/foo/)
true
iex> Regex.regex?(0)
false
Receives a regex, a binary and a replacement, returns a new binary where all matches are replaced by the replacement.
The replacement can be either a string or a function. The string
is used as a replacement for every match and it allows specific
captures to be accessed via \N
or \g{N}
, where N
is the
capture. In case \0
is used, the whole match is inserted. Note
that in regexes the backslash needs to be escaped, hence in practice
you’ll need to use \\N
and \\g{N}
.
When the replacement is a function, the function may have arity
N where each argument maps to a capture, with the first argument
being the whole match. If the function expects more arguments
than captures found, the remaining arguments will receive ""
.
Options
:global
- whenfalse
, replaces only the first occurrence (defaults totrue
)
Examples
iex> Regex.replace(~r/d/, "abc", "d")
"abc"
iex> Regex.replace(~r/b/, "abc", "d")
"adc"
iex> Regex.replace(~r/b/, "abc", "[\\0]")
"a[b]c"
iex> Regex.replace(~r/a(b|d)c/, "abcadc", "[\\1]")
"[b][d]"
iex> Regex.replace(~r/\.(\d)$/, "500.5", ".\\g{1}0")
"500.50"
iex> Regex.replace(~r/a(b|d)c/, "abcadc", fn _, x -> "[#{x}]" end)
"[b][d]"
iex> Regex.replace(~r/a/, "abcadc", "A", global: false)
"Abcadc"
run(t, binary, [term]) :: nil | [binary] | [{integer, integer}]
Runs the regular expression against the given string until the first match.
It returns a list with all captures or nil
if no match occurred.
Options
:return
- sets to:index
to return indexes. Defaults to:binary
.:capture
- what to capture in the result. Check the moduledoc forRegex
to see the possible capture values.
Examples
iex> Regex.run(~r/c(d)/, "abcd")
["cd", "d"]
iex> Regex.run(~r/e/, "abcd")
nil
iex> Regex.run(~r/c(d)/, "abcd", return: :index)
[{2, 2}, {3, 1}]
Same as run/3
, but scans the target several times collecting all
matches of the regular expression.
A list of lists is returned, where each entry in the primary list represents a match and each entry in the secondary list represents the captured contents.
Options
:return
- sets to:index
to return indexes. Defaults to:binary
.:capture
- what to capture in the result. Check the moduledoc forRegex
to see the possible capture values.
Examples
iex> Regex.scan(~r/c(d|e)/, "abcd abce")
[["cd", "d"], ["ce", "e"]]
iex> Regex.scan(~r/c(?:d|e)/, "abcd abce")
[["cd"], ["ce"]]
iex> Regex.scan(~r/e/, "abcd")
[]
iex> Regex.scan(~r/\p{Sc}/u, "$, £, and €")
[["$"], ["£"], ["€"]]
Splits the given target based on the given pattern and in the given number of parts.
Options
:parts
- when specified, splits the string into the given number of parts. If not specified,:parts
defaults to:infinity
, which will split the string into the maximum number of parts possible based on the given pattern.:trim
- whentrue
, removes empty strings (""
) from the result.:on
- specifies which captures to split the string on, and in what order. Defaults to:first
which means captures inside the regex do not affect the splitting process.:include_captures
- whentrue
, includes in the result the matches of the regular expression. Defaults tofalse
.
Examples
iex> Regex.split(~r{-}, "a-b-c")
["a", "b", "c"]
iex> Regex.split(~r{-}, "a-b-c", [parts: 2])
["a", "b-c"]
iex> Regex.split(~r{-}, "abc")
["abc"]
iex> Regex.split(~r{}, "abc")
["a", "b", "c", ""]
iex> Regex.split(~r{a(?<second>b)c}, "abc")
["", ""]
iex> Regex.split(~r{a(?<second>b)c}, "abc", on: [:second])
["a", "c"]
iex> Regex.split(~r{(x)}, "Elixir", include_captures: true)
["Eli", "x", "ir"]
iex> Regex.split(~r{a(?<second>b)c}, "abc", on: [:second], include_captures: true)
["a", "b", "c"]
Returns the version of the underlying Regex engine.