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Re: Race in bash-4.3 'typeset'?

From: Chet Ramey
Subject: Re: Race in bash-4.3 'typeset'?
Date: Fri, 28 Oct 2016 10:00:14 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 10/25/16 12:40 AM, Martijn Dekker wrote:
> Op 25-10-16 om 00:42 schreef Stuart Shelton:
>> Failing this, is there any alternative to ‘typeset’ to list a
>> variable declared as local to a function but which has not yet been
>> assigned a value?
> Try simply testing the exit status of 'typeset -p' or 'declare -p'. If
> the variable is not declared, it exits unsuccessfully.
>     if typeset -p "$var" >/dev/null 2>&1 && [[ ! -v $var ]]
>     then ...
> As far as I can tell, this is not documented in 'help' or in the info
> page, by the way. Perhaps it should be.

It's documented.  The man page, for instance, says:

"The return value is 0 unless ... one of the names is not a valid shell
variable name"

which handles both the "not correctly formed" and "not found" cases.

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/

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