Re: [Help-bash] catching read error conditions

[Steven W. Orr]

On 1/28/2013 10:59 AM, Chet Ramey wrote:
> On 1/28/13 8:32 AM, Greg Wooledge wrote:
>
> > Well, any of the ways of testing the exit status should suffice.
> > Also note that you can't distinguish a failure-due-to-timeout from
> > other kinds of failures.
>
> Not quite true.  The manual says:
>
> "The exit status is greater than 128 if the timeout is exceeded."
>
> That does narrow the error space.
>
> Chet

Which works out very nicely, in that (on my Fedora system) I get an exit 
status of 142. And 142 - 128 is 14. And 14 happens to be the value of SIGALRM. 
Why is this nice? Because, the exit status of a program that exits is less 
than 128 and the exit status of a program that signals out should be 128 + the 
signal that was not caught (as described in The Fine Manual). This also 
applies to simple builtin commands.


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