Re: Fw: awk standard incompatibility

[Paul Eggert]

Denys Vlasenko <address@hidden> writes:

>> http://busybox.net/bugs/view.php?id=914
>>
>> but now it looks like it's gawk being a bit non-standard compliant,

No, gawk and Busybox awk both conform to the standard here.  It's a
bug in the script, which uses the following pattern:

  /^[\t ]*UDK_3_0_0[\t ]*{/

POSIX does not allow this pattern.  See POSIX 1003.1-2004 section 9.4.3
<http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04_03>,
which says that the behavior of an ERE is undefined "if a left-brace
is not part of a valid interval expression".  Hence an awk
implementation can do what it likes with this pattern: Busybox awk can
print a diagnostic, and gawk can treat "{" as if it were "[{]", and
both behaviors conform to the standard.

It is true that gawk does not conform to POSIX in programs like
'/a{3}/ {print}', unless you set the POSIXLY_CORRECT environment
variable or use the --posix option.  However, gawk is in good company
here; e.g., Solaris 10 'nawk' behaves like gawk, not like POSIX.  So,
in practice, portable scripts cannot use unescaped "{" in regular
expressions, even as part of POSIX-blessed interval expressions.