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If you’re programming with Regex, you can set a pattern buffer’s (see GNU Pattern Buffers) syntax either to an arbitrary combination of syntax bits (see Syntax Bits) or else to the configurations defined by Regex. These configurations define the syntaxes used by certain programs—GNU Emacs, POSIX Awk, traditional Awk, Grep, Egrep—in addition to syntaxes for POSIX basic and extended regular expressions.
The predefined syntaxes—taken directly from regex.h—are:
#define RE_SYNTAX_EMACS 0 #define RE_SYNTAX_AWK \ (RE_BACKSLASH_ESCAPE_IN_LISTS | RE_DOT_NOT_NULL \ | RE_NO_BK_PARENS | RE_NO_BK_REFS \ | RE_NO_BK_VBAR | RE_NO_EMPTY_RANGES \ | RE_UNMATCHED_RIGHT_PAREN_ORD) #define RE_SYNTAX_POSIX_AWK \ (RE_SYNTAX_POSIX_EXTENDED | RE_BACKSLASH_ESCAPE_IN_LISTS) #define RE_SYNTAX_GREP \ (RE_BK_PLUS_QM | RE_CHAR_CLASSES \ | RE_HAT_LISTS_NOT_NEWLINE | RE_INTERVALS \ | RE_NEWLINE_ALT) #define RE_SYNTAX_EGREP \ (RE_CHAR_CLASSES | RE_CONTEXT_INDEP_ANCHORS \ | RE_CONTEXT_INDEP_OPS | RE_HAT_LISTS_NOT_NEWLINE \ | RE_NEWLINE_ALT | RE_NO_BK_PARENS \ | RE_NO_BK_VBAR) #define RE_SYNTAX_POSIX_EGREP \ (RE_SYNTAX_EGREP | RE_INTERVALS | RE_NO_BK_BRACES) /* P1003.2/D11.2, section 4.20.7.1, lines 5078ff. */ #define RE_SYNTAX_ED RE_SYNTAX_POSIX_BASIC #define RE_SYNTAX_SED RE_SYNTAX_POSIX_BASIC /* Syntax bits common to both basic and extended POSIX regex syntax. */ #define _RE_SYNTAX_POSIX_COMMON \ (RE_CHAR_CLASSES | RE_DOT_NEWLINE | RE_DOT_NOT_NULL \ | RE_INTERVALS | RE_NO_EMPTY_RANGES) #define RE_SYNTAX_POSIX_BASIC \ (_RE_SYNTAX_POSIX_COMMON | RE_BK_PLUS_QM) /* Differs from ..._POSIX_BASIC only in that RE_BK_PLUS_QM becomes RE_LIMITED_OPS, i.e., \? \+ \| are not recognized. Actually, this isn't minimal, since other operators, such as \`, aren't disabled. */ #define RE_SYNTAX_POSIX_MINIMAL_BASIC \ (_RE_SYNTAX_POSIX_COMMON | RE_LIMITED_OPS) #define RE_SYNTAX_POSIX_EXTENDED \ (_RE_SYNTAX_POSIX_COMMON | RE_CONTEXT_INDEP_ANCHORS \ | RE_CONTEXT_INDEP_OPS | RE_NO_BK_BRACES \ | RE_NO_BK_PARENS | RE_NO_BK_VBAR \ | RE_UNMATCHED_RIGHT_PAREN_ORD) /* Differs from ..._POSIX_EXTENDED in that RE_CONTEXT_INVALID_OPS replaces RE_CONTEXT_INDEP_OPS and RE_NO_BK_REFS is added. */ #define RE_SYNTAX_POSIX_MINIMAL_EXTENDED \ (_RE_SYNTAX_POSIX_COMMON | RE_CONTEXT_INDEP_ANCHORS \ | RE_CONTEXT_INVALID_OPS | RE_NO_BK_BRACES \ | RE_NO_BK_PARENS | RE_NO_BK_REFS \ | RE_NO_BK_VBAR | RE_UNMATCHED_RIGHT_PAREN_ORD)