Martin Langhoff <[email protected]> wrote: > The flock binary in modern linuxes (from util-linux-ng) supports > flocking a filehandle that is handled by the shell. Combining this > with per-code-block filehandles / io redirection, it is an incredibly > useful construct to protect a code block with a lock. > > The resulting code looks like this (from man flock on Fedora 11): > > ( > flock -s 200 > # ... commands executed under lock ... > ) 200>/var/lock/mylockfile > > I am now discovering that this works in bash, but not in dash. > > Is there a posixly correct way to do this? Can dash handle it? Is > there a syntax for this that is both dash and bash friendly? > > If the answer is not -- this codepath is conditional. Is there a way > for me to test for which shell is running (and only attempt it under > bash)?
POSIX only requires file descriptors 0-9 for shell redirections. So if you replace 200 with 9 it should work assuming that nothing within the block uses fd 9. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[email protected]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe dash" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
