OS X sed -E non accetta espressioni regolari estese

Ho provato vari modi per fare alcune cose di base con sed su OS X. Ecco i risultati di alcuni semplici test.

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

ritorni (come previsto)

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

ma

 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' 

ritorna

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

e (ancora più irritantemente)

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

ritorna

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

Ora, le pagine man sed dicono questo

 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. 

e l’ man re_format dice

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

E senza dubbio:

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

mi da

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

… ma questo è fastidioso. O perché sono denso, o perché le pagine man mi stanno mentendo (ad essere sincero, preferirei il primo).

Una rapida rassegna bibliografica qui su SO suggerisce che non sono solo in questo, e che molti raccomandano l’installazione di GNU coreutils (o effettivamente usano qualcos’altro – ad esempio perl -pe ) – tuttavia, mi piacerebbe essere sicuro:

Do ERE funziona con sed come è in bundle con OS X – come implicito nelle pagine man – o no?

(Sono su 10.8 e 10.6.8)

Le ERE (Extended Regular Expressions) sono descritte in POSIX sotto (a sorpresa) Regular Expressions o su Mac OS X sotto man re_format . Gli ERE non usano la notazione in stile PCRE \d per indicare la cifra.

Dovrai usare [0-9] o [[:digit:]] per indicare la cifra.

 $ 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 $ 

Che ne dici di \ d?

Sul mio Mac OS X (10.7.4), l’ man re_format non dice nulla su \d cifre corrispondenti.

 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, eg `[0-9]' in ASCII matches any decimal digit. It is illegal= for two ranges to share an endpoint, eg `ac-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, eg 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 classs 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 transformsd into a bracket expres- sion containing both cases, eg `x' becomes `[xX]'. When it appears inside a bracket expression, all case counterparts of it are added to the bracket expression, so that (eg) `[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 (eg) `\([bc]\)\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 

Su OS X, \d fa parte di un set di funzioni regex chiamato funzioni avanzate : notare la distinzione nel nome: enhanced , che NON è la stessa di extended .

Invece, le funzionalità avanzate sono una dimensione separata da base a estesa che può essere triggersta sia per le espressioni regolari sia per quelle di base. In altre parole: puoi avere regex di base migliorate e regex estese avanzate .

Tuttavia, sembra che le funzionalità avanzate disponibili in un dato programma di utilità siano precompilate in esso ; in altre parole: un dato programma di utilità supporta le funzionalità avanzate o no – nessuna opzione può cambiarlo . (Le opzioni ti consentono solo di scegliere tra base ed estesa, come ad esempio -E per sed e grep .)

Per una descrizione di tutte le funzionalità avanzate , vedere la sezione ENHANCED FEATURES in man re_format .

Va inoltre notato che se la compatibilità POSIX è importante, le funzionalità avanzate dovrebbero essere evitate con sed .
Esistono utilità POSIX, come awk , che supportano ERE (espressioni regolari estese), ma (a), le specifiche POSIX devono esplicitamente dichiararlo, e (b) la syntax è limitata a POSIX ERE , che sono meno potenti di l’offerta di piattaforms specifiche ERE.


In pratica:

Purtroppo, le pagine man per le varie utilità NON indicano se una determinata utility supporta funzionalità regex avanzate, quindi si tratta di tentativi ed errori.

A partire da OS X 10.10.1 :

OS X sed NON supporta funzionalità avanzate , il che spiega l’esperienza dell’OP.

Ho trovato solo 1 utility che supporta funzionalità avanzate: grep :

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

Se conosci qualcuno che lo fa, per favore fammelo sapere.