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Quoting near =~ is inconsistent

From: Kevin F. Quinn
Subject: Quoting near =~ is inconsistent
Date: Sun, 14 Jan 2007 20:25:54 +0100

Configuration Information [Automatically generated, do not change]:
Machine: i686
OS: linux-gnu
Compiler: i686-pc-linux-gnu-gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i686'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i686-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
-DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib   -ggdb2 -O2
-march=pentium3 -pipe -Wall -Wstack-protector -Wtrampolines uname
output: Linux c1358217 2.6.18-hardened #4 PREEMPT Wed Dec 20 23:25:36
CET 2006 i686 Mobile Intel(R) Pentium(R) III CPU - M  1200MHz
GenuineIntel GNU/Linux Machine Type: i686-pc-linux-gnu

Bash Version: 3.2
Patch Level: 9
Release Status: release

    Matching on =~ is inconsistent with == et. al.
    I see there's a FAQ entry mentioning that the rhs of =~ is
    automatically interpreted as a string, but I don't think
    it means the behaviour below is expected.  It means the only
    way of expressing strings containing characters meaningful
    to the shell, is to escape them.  The behaviour in bash-3.1
    is consistent with other comparison operators.  It seems that
    with '=~', quotes on a literal string in the rhs are considered
    part of the text to match - traditionally I'd have written that
    by escaping the quotes if I wanted to match them.

    $ v="Alphabet"
    $ [[ ${v} == "Alphabet" ]] && echo matches
    $ [[ ${v} == 'Alphabet' ]] && echo matches
    $ [[ ${v} == Alphabet ]] && echo matches
    $ [[ ${v} =~ "Alphabet" ]] && echo matches
    $ [[ ${v} =~ 'Alphabet' ]] && echo matches
    $ [[ ${v} =~ Alphabet ]] && echo matches
    $ v="one two buckle my shoe"
    $ [[ ${v} =~ "one two" ]] && echo matches
    $ [[ ${v} =~ one two ]] && echo matches
    <syntax error, obviously>
    $ [[ ${v} =~ one\ two ]] && echo matches

Kevin F. Quinn

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