XPost: uk.comp.os.linux   
   From: chris@internal.net   
      
   On 11/09/2025 at 11:02, Mike Scott wrote:   
   > On 11/09/2025 08:49, Richard Kettlewell wrote:   
   >> Mike Scott  writes:   
   >>> On 10/09/2025 09:42, Dan Purgert wrote:   
   >>>> On 2025-09-10, Mike Scott wrote:   
   >>>>> On 04/09/2025 08:26, Richard Kettlewell wrote:   
   >>>>>> Mike Scott>>>> ottsonline.org.uk.invalid> writes:   
   >>>>>>> I've been using a program 'daemon' on freebsd   
   >>>>>>> (eg   
   >>>>>>> man.freebsd.org/cgi/man.cgi?query=daemon&sektion=8&manpa   
   h=FreeBSD+14.3-RELEASE+and+Ports)   
   >>>>>>>   
   >>>>>>>   
   >>>>>>> which will run arbitrary programs as daemons, handling all the   
   >>>>>>> necessary "house-keeping" for them.   
   >>>>>>>   
   >>>>>>> I can't find a ready-to-roll linux version - is there one please?   
   >>>>>> If you want an (almost) identical interface then in Debian (and   
   >>>>>> presumably therefore also Ubuntu), there’s a command of the same name   
   >>>>>> and similar behavior:   
   >>>>>>   
   >>>>>> https://manpages.debian.org/trixie/daemon/daemon.1.en.html   
   >>>>>   
   >>>>> Sorry, back again.   
   >>>>>   
   >>>>> I've been playing with this and there seems to be an important feature   
   >>>>> missing on linux that's in the BSD version: how to do logfile   
   >>>>> rotation?   
   >>>>> [...]   
   >>>>> Have I missed something?   
   >>>> logrotate(8) ?   
   >>>   
   >>> Thanks for the reply, but no. That assumes the existence of the   
   >>> mechanism missing AFAICS from this daemon.   
   >>>   
   >>> And to answer ldo, this is for a web daemon that writes its own   
   >>> private log file that needs archival copies kept; syslog is not   
   >>> appropriate. I've been doing that using mv and sending the BSD daemon   
   >>> a sighup; migration is being something of a chore.   
   >>>   
   >>> Looks like I'll have to see about patching the daemon source code.   
   >>   
   >> I’m not quite clear on the requirement here. I think what you mean is:   
   >>   
   >> * The daemon executable logs to stdout and/or stderr   
   >> * You want these logs saved to a file   
   >> * You want this file rotated (in the normal way for a logfile)   
   >> * You want to keep the data essentially indefinitely, or at least, for   
   >>    longer than other syslog outputs.   
   >>   
   >> I can see several options.   
   >>   
   >> 1) Change the daemon to log to the target file instead of stdout/stderr,   
   >>     and either arrange for it to close and re-open the logfile when it   
   >>     recieves SIGHUP, or just do the log rotate itself (which avoids   
   >>     dealing with signal handlers).   
   >>   
   >> 2) Add a second program that reads from stdin and writes to the target   
   >>     logfile, doing the log rotation itself. The daemon command line would   
   >>     be a pipeline, e.g. daemon sh -c "executable 2>&1 | loghandler".   
   >>   
   >> 3) Log to syslog, either directly or via the daemon wrapper. syslog   
   >>     daemons (e.g. rsyslogd) can select a specific program’s logs to an   
   >>     individual file, and you can control the log rotation policy for that   
   >>     file individually. The syslog daemon takes care of the close/re-open   
   >>     dance.   
   >>   
   >   
   > The problem is fixed to my satisfaction, but to answer your query.   
   >   
   > The target program runs unattended for extended periods. It writes a lot   
   > of data to stdout and stderr. It is not of itself a daemon in the linux   
   > sense, just a large chunk of perl code that normally runs at a terminal.   
   > To make it a self-contained linux daemon would be a pain, and pointless   
   > duplication of code. At user-determined intervals, I need output to be   
   > directed to a fresh file.   
   >   
   > On freebsd, I've been using a program called 'daemon'. This runs the   
   > target program as a child process, intercepting its stdout and stderr   
   > and writing their data to a suitable file; it also does the necessary   
   > detaching and other housekeeping operations on its behalf. Importantly,   
   > 'daemon' responds to a suitable signal by closing and reopening its   
   > output. This provides a way of chopping up the target program's output   
   > streams into files for archiving and further processing without stopping   
   > it.   
   >   
   > The linux program of the same name does much the same - but lacks the   
   > ability to close and reopen its output files. 'logrotate' can sort-of   
   > work around this with a (small) risk of data loss for programs like   
   > mine, that cannot handle rotation hygienically.   
   >   
   > I've now modified the linux 'daemon' program to respond as the freebsd   
   > one, and it can now close and reopen its output file(s) without risk of   
   > data loss. So archiving now becomes a simple matter of "mv log.txt   
   > log.old; kill -usr2 " which results in log.old with the data   
   > to date, and a fresh log.txt being opened.   
   >   
   > I've emailed the author to see if he's interested in rolling the   
   > modification into the next release.   
   >   
   > And yes, I suppose your suggestion #2 would have worked. But involving a   
   > 3rd program is messy, and I'd still be having cut code to tell it to do   
   > the log rotation on request. Better to put that where it really belongs,   
   > I think. But thanks for the idea.   
   >   
   >   
   >   
      
   Have you seen 'daemonize' - seems to do what you want.   
      
      
   --   
   Chris Elvidge, England   
   ALL WORK AND NO PLAY MAKES BART A DULL BOY   
   Bart Simpson on chalkboard in episode 1F07   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)