On 6/14/16 8:52 AM, Néstor Tejero wrote:
> When printing a multi-line string and piping to another command that uses
> single-quotes, Bash tries to perform history expansion:
>
> echo "9
>> 10
>> 9
>> 11" | awk '!seen[$0]++'
> bash: !seen[$0]++': event not found
History expansion is explicitly line-oriented. It doesn't know about shell
state, especially shell quoting state, that spans lines. It does know about
vaguely shell-like quoting that's common across a large set of Unix
utilities -- since the history and readline libraries are used outside the
shell -- and that a double quote introduces a quoted string in which
single quotes are not significant and don't inhibit history expansion.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU [email protected] http://cnswww.cns.cwru.edu/~chet/
