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Re: avoid mktemp/mkstemp internally


From: Chet Ramey
Subject: Re: avoid mktemp/mkstemp internally
Date: Mon, 16 May 2016 10:02:33 -0400
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On 5/13/16 2:40 PM, Mike Frysinger wrote:
> i was pointed at a bug report for FreeBSD systems [1] where running lots
> of processes in parallel would randomly fail with errors like:
>   cannot make pipe for process substitution: File exists
> 
> upstream FreeBSD addressed this by defining USE_MKTEMP [2] & USE_MKSTEMP
> [3] when building bash.  looking at the source in bash though, i can't
> see why these aren't always defined.  why does bash try to reimplement
> both funcs ad-hoc instead of just using the stable/guaranteed system
> versions ?

Because many traditional implementations of mktemp/mkstemp suck.

> the bash versions seem like it's pretty trivial to collide: it mixes
> current seconds count, current pid number, and a counter. 

Not quite; the calls in bash mix in the return value from the system's
random().  Now, if that sucks too, you're going to lose.

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

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