The GNU C Library - Flags for POSIX Regexps

Flags for POSIX Regular Expressions

These are the bit flags that you can use in the cflags operand when compiling a regular expression with regcomp .

REG_EXTENDED

Treat the pattern as an extended regular expression, rather than as a basic regular expression.

REG_ICASE

Ignore case when matching letters.

REG_NOSUB

Don't bother storing the contents of the matches-ptr array.

REG_NEWLINE

Treat a newline in string as dividing string into multiple lines, so that `$' can match before the newline and `^' can match after. Also, don't permit `.' to match a newline, and don't permit `[^...]' to match a newline.

Otherwise, newline acts like any other ordinary character.