Thanks Clark, that isclear. I hadn't thought to look at the ksh man page
for trap. However, the trap manual is not clear about this behaviour and
could do with updating. Currently (Version jM 93u 2011-02-08) it only
states: "If action is -, trap resets each condition to the default
value. If action is an empty string, the shell ignores each of the
conditions if they arise. "
Cheers, Gerald
On 19/08/2014 8:35 p.m., clarkw wrote:
On Tue, Aug 19, 2014 at 10:54 AM, gerald cato <[email protected]
<mailto:[email protected]>> wrote:
Hi,
I've noticed inconsistent behavior between trap <number> vs trap
<name> when action is null. For example:
$ Version jM 93u 2011-02-08
$ trap '' 0
$ trap 0
$ trap '' exit
$ trap exit
ksh: trap: condition(s) required
$ trap '' 1
$ trap 1
$ trap '' HUP
$ trap HUP
ksh: trap: condition(s) required
$
According to the ksh(1) manual (Version jM 93u 2011-02-08), "If
/action/ is omitted and the first /sig/ is a number, or if /action/ is
-, then the trap(s) for each /sig/ are reset to their original
values". So both `trap exit' and `trap HUP' are invalid commands as
"exit" and "HUP" are not numbers.
-clark
$ Version M-11/16/88i
$ trap '' exit
$ trap '' 0
$ trap exit
$ trap 0
Not sure if this has been fixed in a later release.
Cheers, Gerald
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