On 8/28/19 2:16 AM, ak...@free.fr wrote: > Hi, > I encounter some problem with grep option -E on cygwin 3.0.7 > > > echo "a^b" | grep "a^b" #answer a^b ie it's OK
POSIX says: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html "A BRE special character has special properties in certain contexts. Outside those contexts, or when preceded by a <backslash>, such a character is a BRE that matches the special character itself." ... "A <circumflex> ( '^' ) shall be an anchor when used as the first character of an entire BRE. The implementation may treat the <circumflex> as an anchor when used as the first character of a subexpression." Since ^ is only special as the first character or in a [], and you have used it for neither, this is a well-specified literal match. > but > echo "a^b" | grep -E "a^b" #answer nothing " for me it's KO "An ERE special character has special properties in certain contexts. Outside those contexts, or when preceded by a <backslash>, such a character shall be an ERE that matches the special character itself." "A <circumflex> ( '^' ) outside a bracket expression shall anchor the expression or subexpression it begins to the beginning of a string; such an expression or subexpression can match only a sequence starting at the first character of a string. For example, the EREs "^ab" and "(^ab)" match "ab" in the string "abcdef", but fail to match in the string "cdefab", and the ERE "a^b" is valid, but can never match because the 'a' prevents the expression "^b" from matching starting at the first character." So in ERE, ^ is an anchor anywhere, while in BRE, ^ is an anchor only as the first byte. The difference you are observing matches POSIX. > > > I have to backslash ^ to be OK like : grep -E 'a\^b' Correct. > > > Is-it a bug ? No. (In fact, if you test on Linux, you'll see the same behavior, which shows it is not specific to Cygwin). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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