OS X sed -E不接受扩展正则表达式

Question

我一直在尝试各种方法来使用OS X上的sed做一些基本的事情.以下是一些简单测试的结果.

echo "foo bar 2011-03-17 17:31:47 foo bar" | sed 's/foo/FOUND/g'

返回(按预期)

FOUND bar 2011-03-17 17:31:47 FOUND bar

但

echo "foo bar 2011-03-17 17:31:47 foo bar" | sed -E 's/\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}/FOUND/g'

回报

foo bar 2011-03-17 17:31:47 foo bar

(甚至更刺激)

echo "food bar 2011-03-17 17:31:47 food bar" | sed -E 's/\d/FOUND/g'

回报

fooFOUND bar 2011-03-17 17:31:47 fooFOUND bar

现在,man sed页面说明了这一点

The following options are available:

 -E      Interpret regular expressions as extended (modern) regular
         expressions rather than basic regular expressions (BRE's).  The
         re_format(7) manual page fully describes both formats.

并man re_format说

          \d  Matches a digit character.  This is equivalent to
          `[[:digit:]]'.

事实上:

echo "foo bar 2011-03-17 17:31:47 foo bar" | sed -E 's/[[:digit:]]{4}/FOUND/g'

给我

foo bar FOUND-03-17 17:31:47 foo bar

......但这很烦人.无论是因为我是密集的,还是因为手册对我说谎(说实话,我更喜欢前者).

一篇关于SO的快速文献综述表明,我并不孤单,并且许多人建议安装GNU coreutils(或者确实使用别的东西 - 比如说perl -pe) - 但是,我想确定:

ERE sed是否与OS X捆绑在一起 - 正如man页面所暗示的那样- 或不是？

(我在10.8和10.6.8)

Answer 1

在OS X上,\d是名为增强功能的正则表达式功能集的一部分 - 请注意名称中的区别:增强,与扩展功能不同.

相反,增强的特征是从单独的维度基本与扩展,可以为被激活两个基本和扩展的正则表达式.换句话说:您可以使用增强的基本正则表达式以及增强的扩展正则表达式.

但是,似乎在给定实用程序中是否可以使用增强功能进行预编译 ; 换句话说:给定的实用程序要么支持增强功能,要么不支持- 没有选项可以改变它.(选项只允许您在基本和扩展之间进行选择,例如-Efor sed和grep.)

对于所有增强功能的说明,请参见ENHANCED FEATURES在man re_format.

还应注意,如果POSIX兼容性很重要,则应避免使用增强功能sed.
^{这里是 POSIX实用程序,如awk,该做支持ERES(扩展的正则表达式),但(一),在POSIX规范明确有状态,因此,和(b)的语法限制为POSIX ERES,这是不那么强大的比ERE特定平台提供.}

在实践中:

遗憾的是,man各种实用程序的页面并未说明给定的实用程序是否支持增强的正则表达式功能,因此它归结为试验和错误.

从OS X 10.10.1开始:

OS X sed不支持增强功能,这解释了OP的经验.

我发现只有1个实用程序支持增强功能grep:

grep    -o '\d\+' <<<'a10' # -> '10' - enhanced basic regex
grep -E -o '\d+'  <<<'a10' # -> '10' - enhanced extended regex

如果你知道有其他人这样做,请告诉我.

Answer 2

ERE(扩展正则表达式)在POSIX(惊喜)正则表达式或Mac OS X下描述man re_format.ERE不使用PCRE样式\d表示法来表示数字.

您将需要使用[0-9]或[[:digit:]]表示数字.

$ echo "foo bar 2011-03-17 17:31:47 foo bar" |
> sed -E 's/[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}/FOUND/g'
foo bar FOUND foo bar
$ echo "foo bar 2011-03-17 17:31:47 foo bar" |
> sed -E 's/[[:digit:]]{4}-[[:digit:]]{2}-[[:digit:]]{2} [[:digit:]]{2}:[[:digit:]]{2}:[[:digit:]]{2}/FOUND/g'
foo bar FOUND foo bar
$

\ d怎么样？

在我的Mac OS X(10.7.4)上,man re_format没有说明\d匹配数字.

RE_FORMAT(7)         BSD Miscellaneous Information Manual     RE_FORMAT(7)

NAME
     re_format -- POSIX 1003.2 regular expressions

DESCRIPTION
     Regular expressions (``REs''), as defined in IEEE Std 1003.2
     (``POSIX.2''), come in two forms: modern REs (roughly those of egrep(1);
     1003.2 calls these ``extended'' REs) and obsolete REs (roughly those of
     ed(1); 1003.2 ``basic'' REs).  Obsolete REs mostly exist for backward
     compatibility in some old programs; they will be discussed at the end.
     IEEE Std 1003.2 (``POSIX.2'') leaves some aspects of RE syntax and seman-
     tics open; `=' marks decisions on these aspects that may not be fully
     portable to other IEEE Std 1003.2 (``POSIX.2'') implementations.

     A (modern) RE is one= or more non-empty= branches, separated by `|'.  It
     matches anything that matches one of the branches.

     A branch is one= or more pieces, concatenated.  It matches a match for
     the first, followed by a match for the second, etc.

     A piece is an atom possibly followed by a single= `*', `+', `?', or
     bound.  An atom followed by `*' matches a sequence of 0 or more matches
     of the atom.  An atom followed by `+' matches a sequence of 1 or more
     matches of the atom.  An atom followed by `?' matches a sequence of 0 or
     1 matches of the atom.

     A bound is `{' followed by an unsigned decimal integer, possibly followed
     by `,' possibly followed by another unsigned decimal integer, always fol-
     lowed by `}'.  The integers must lie between 0 and RE_DUP_MAX (255=)
     inclusive, and if there are two of them, the first may not exceed the
     second.  An atom followed by a bound containing one integer i and no
     comma matches a sequence of exactly i matches of the atom.  An atom fol-
     lowed by a bound containing one integer i and a comma matches a sequence
     of i or more matches of the atom.  An atom followed by a bound containing
     two integers i and j matches a sequence of i through j (inclusive)
     matches of the atom.

     An atom is a regular expression enclosed in `()' (matching a match for
     the regular expression), an empty set of `()' (matching the null
     string)=, a bracket expression (see below), `.' (matching any single
     character), `^' (matching the null string at the beginning of a line),
     `$' (matching the null string at the end of a line), a `\' followed by
     one of the characters `^.[$()|*+?{\' (matching that character taken as an
     ordinary character), a `\' followed by any other character= (matching
     that character taken as an ordinary character, as if the `\' had not been
     present=), or a single character with no other significance (matching
     that character).  A `{' followed by a character other than a digit is an
     ordinary character, not the beginning of a bound=.  It is illegal to end
     an RE with `\'.

     A bracket expression is a list of characters enclosed in `[]'.  It nor-
     mally matches any single character from the list (but see below).  If the
     list begins with `^', it matches any single character (but see below) not
     from the rest of the list.  If two characters in the list are separated
     by `-', this is shorthand for the full range of characters between those
     two (inclusive) in the collating sequence, e.g. `[0-9]' in ASCII matches
     any decimal digit.  It is illegal= for two ranges to share an endpoint,
     e.g. `a-c-e'.  Ranges are very collating-sequence-dependent, and portable
     programs should avoid relying on them.

     To include a literal `]' in the list, make it the first character (fol-
     lowing a possible `^').  To include a literal `-', make it the first or
     last character, or the second endpoint of a range.  To use a literal `-'
     as the first endpoint of a range, enclose it in `[.' and `.]' to make it
     a collating element (see below).  With the exception of these and some
     combinations using `[' (see next paragraphs), all other special charac-
     ters, including `\', lose their special significance within a bracket
     expression.

     Within a bracket expression, a collating element (a character, a multi-
     character sequence that collates as if it were a single character, or a
     collating-sequence name for either) enclosed in `[.' and `.]' stands for
     the sequence of characters of that collating element.  The sequence is a
     single element of the bracket expression's list.  A bracket expression
     containing a multi-character collating element can thus match more than
     one character, e.g. if the collating sequence includes a `ch' collating
     element, then the RE `[[.ch.]]*c' matches the first five characters of
     `chchcc'.

     Within a bracket expression, a collating element enclosed in `[=' and
     `=]' is an equivalence class, standing for the sequences of characters of
     all collating elements equivalent to that one, including itself.  (If
     there are no other equivalent collating elements, the treatment is as if
     the enclosing delimiters were `[.' and `.]'.)  For example, if `x' and
     `y' are the members of an equivalence class, then `[[=x=]]', `[[=y=]]',
     and `[xy]' are all synonymous.  An equivalence class may not= be an end-
     point of a range.

     Within a bracket expression, the name of a character class enclosed in
     `[:' and `:]' stands for the list of all characters belonging to that
     class.  Standard character class names are:

       alnum    digit    punct
       alpha    graph    space
       blank    lower    upper
       cntrl    print    xdigit

     These stand for the character classes defined in ctype(3).  A locale may
     provide others.  A character class may not be used as an endpoint of a
     range.

     A bracketed expression like `[[:class:]]' can be used to match a single
     character that belongs to a character class.  The reverse, matching any
     character that does not belong to a specific class, the negation operator
     of bracket expressions may be used: `[^[:class:]]'.

     There are two special cases= of bracket expressions: the bracket expres-
     sions `[[:<:]]' and `[[:>:]]' match the null string at the beginning and
     end of a word respectively.  A word is defined as a sequence of word
     characters which is neither preceded nor followed by word characters.  A
     word character is an alnum character (as defined by ctype(3)) or an
     underscore.  This is an extension, compatible with but not specified by
     IEEE Std 1003.2 (``POSIX.2''), and should be used with caution in soft-
     ware intended to be portable to other systems.

     In the event that an RE could match more than one substring of a given
     string, the RE matches the one starting earliest in the string.  If the
     RE could match more than one substring starting at that point, it matches
     the longest.  Subexpressions also match the longest possible substrings,
     subject to the constraint that the whole match be as long as possible,
     with subexpressions starting earlier in the RE taking priority over ones
     starting later.  Note that higher-level subexpressions thus take priority
     over their lower-level component subexpressions.

     Match lengths are measured in characters, not collating elements.  A null
     string is considered longer than no match at all.  For example, `bb*'
     matches the three middle characters of `abbbc',
     `(wee|week)(knights|nights)' matches all ten characters of `weeknights',
     when `(.*).*' is matched against `abc' the parenthesized subexpression
     matches all three characters, and when `(a*)*' is matched against `bc'
     both the whole RE and the parenthesized subexpression match the null
     string.

     If case-independent matching is specified, the effect is much as if all
     case distinctions had vanished from the alphabet.  When an alphabetic
     that exists in multiple cases appears as an ordinary character outside a
     bracket expression, it is effectively transformed into a bracket expres-
     sion containing both cases, e.g. `x' becomes `[xX]'.  When it appears
     inside a bracket expression, all case counterparts of it are added to the
     bracket expression, so that (e.g.)  `[x]' becomes `[xX]' and `[^x]'
     becomes `[^xX]'.

     No particular limit is imposed on the length of REs=.  Programs intended
     to be portable should not employ REs longer than 256 bytes, as an imple-
     mentation can refuse to accept such REs and remain POSIX-compliant.

     Obsolete (``basic'') regular expressions differ in several respects.  `|'
     is an ordinary character and there is no equivalent for its functional-
     ity.  `+' and `?' are ordinary characters, and their functionality can be
     expressed using bounds (`{1,}' or `{0,1}' respectively).  Also note that
     `x+' in modern REs is equivalent to `xx*'.  The delimiters for bounds are
     `\{' and `\}', with `{' and `}' by themselves ordinary characters.  The
     parentheses for nested subexpressions are `\(' and `\)', with `(' and `)'
     by themselves ordinary characters.  `^' is an ordinary character except
     at the beginning of the RE or= the beginning of a parenthesized subex-
     pression, `$' is an ordinary character except at the end of the RE or=
     the end of a parenthesized subexpression, and `*' is an ordinary charac-
     ter if it appears at the beginning of the RE or the beginning of a paren-
     thesized subexpression (after a possible leading `^').  Finally, there is
     one new type of atom, a back reference: `\' followed by a non-zero deci-
     mal digit d matches the same sequence of characters matched by the dth
     parenthesized subexpression (numbering subexpressions by the positions of
     their opening parentheses, left to right), so that (e.g.)  `\([bc]\)\1'
     matches `bb' or `cc' but not `bc'.

SEE ALSO
     regex(3)

     Regular Expression Notation, IEEE Std, 1003.2, section 2.8.

BUGS
     Having two kinds of REs is a botch.

     The current IEEE Std 1003.2 (``POSIX.2'') spec says that `)' is an ordi-
     nary character in the absence of an unmatched `('; this was an uninten-
     tional result of a wording error, and change is likely.  Avoid relying on
     it.

     Back references are a dreadful botch, posing major problems for efficient
     implementations.  They are also somewhat vaguely defined (does
     `a\(\(b\)*\2\)*d' match `abbbd'?).  Avoid using them.

     IEEE Std 1003.2 (``POSIX.2'') specification of case-independent matching
     is vague.  The ``one case implies all cases'' definition given above is
     current consensus among implementors as to the right interpretation.

     The syntax for word boundaries is incredibly ugly.

BSD             March 20, 1994                 BSD