The grep 2.7 man page has, in the section "REGULAR EXPRESSIONS":
Repetition
A regular expression may be followed by one of several repetition
operators:
...
{,m} The preceding item is matched at most m times.
As far as I know, that format is not standard, and in any case, it seems that
grep rejects it, or it doesn't work as expected:
$ echo 'abbbbc' | grep 'b\{,4\}'
src/grep: malformed repeat count
$ echo 'abbbbc' | grep -E 'b{,4}'
$
$ echo 'abbbbc' | grep -E 'b{,1}'
$
$ grep --version
grep (GNU grep) 2.7
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by Mike Haertel and others, see
<http://git.sv.gnu.org/cgit/grep.git/tree/AUTHORS>.
--
D.
