On Monday 12 March 2007, Nish Aravamudan wrote: >On 3/12/07, Gene Heskett <[EMAIL PROTECTED]> wrote: >> On Monday 12 March 2007, Douglas McNaught wrote: >> >Patrick Mau <[EMAIL PROTECTED]> writes: >> >> Why not temporarly replace "/bin/tar" with a shell script that >> >> does: >> >> >> >> #!/bin/sh >> >> exec strace -f -o output /bin/real.tar $@ >> > >> >You beat me to it. :) I've done that before; it's a great >> > suggestion. >> > >> >Except that if you expect 'tar' to be invoked multiple times in a >> > run, you should probably use 'output.$$' for the output filename so >> > things don't get clobbered. >> > >> >-Doug >> >> In my case, Doug, it will get invoked 64 times, amanda does a dummy >> run to get an estimate, calculates what to do based on that output >> which is 32 runs, 1 per disklist entry and I have 32, and then reruns >> tar with the appropriate level options against each individual >> disklist entry. >> >> But I'm puzzled a bit, what does the double $$ do?, or it buried >> someplace in the bash manpage? Its not something I've stumbled over >> yet. > >buried indeed: > >"Special Parameters: > ... > $ Expands to the process ID of the shell. In a () > subshell, it expands to the process ID of the current shell, not > the sub‐ shell. >"
Well, that's clear enough, but what of the double $$ case? Would this them make a PID unique to each invocation untill it finally wraps a 16 bit value, or will the kernel re-use them because they won't all be running simultainiously, but limited by the number of unique 'spindle' numbers on the system, this to prevent as best as it can, the thrashing of a drive by having tar working on 2 separate (or more) partitions at the same time. In my case 2 are possible, as /var is on a separate drive. >Thanks, >Nish -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) "Say yur prayers, yuh flea-pickin' varmint!" -- Yosemite Sam - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
