Date: Mon, 9 Oct 2006 18:56:19 -0700 (PDT) From: David Thompson <dat1965@yahoo.com> To: Yar Tikhiy <yar@comp.chem.msu.su>, freebsd-rc@freebsd.org Subject: Re: Revised article on rc.d Message-ID: <20061010015619.3492.qmail@web55109.mail.re4.yahoo.com> In-Reply-To: <20061009122342.GB2805@comp.chem.msu.su>
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--- Yar Tikhiy <yar@comp.chem.msu.su> wrote: > After a long delay, I got down to my article on rc.d again. Many > thanks to Gary W. Swearingen for his valuable remarks. The new > version is available at http://people.freebsd.org/~yar/rcng/ . I > think this version can be added to our articles collection after a > few corrections that may be suggested by the readers. ;-) Regarding this paragraph, Note: An rc.d script must be written in the sh(1) language. It cannot be a binary executable because rc.d can opt to feed such scripts into a single instance of sh(1) instead of running each of them separately. This is controlled by an rc.conf(5) variable named rc_fast_and_loose. An rc.d script cannot be written in awk(1) or an interpreted language from ports for the same reason; in addition, it must be runnable early in the system startup sequence, before /usr has been mounted. This caveat is not really true in the strict technical sense. Consider if someone adds this line to their /etc/rc.d script, # KEYWORD: nostart then /etc/rc will not execute this script since rcorder is invoked with '-s nostart'. Thus the reasoning due to the $rc_fast_and_loose variable is not strictly accurate. That is, a script could technically be written in any interpreted language that happens to use '#' as its comment character; as long as the above comment line was added to the script. The problem is, of course, such scripts have to provide their own scaffolding, since rc.subr is written in sh(1); and the script cannot be run directly by /etc/rc due to the use of the sh(1) dot '.' operator (thus it needs 'KEYWORD: nostart' so that /etc/rc will skip it). Although not exactly clear in the above paragraph, the reason files in /etc/rc.d cannot be binary is because rc.d uses the sh(1) dot '.' operator *for all* invocations, like this, if [ -n "$rc_fast_and_loose" ]; then set $_arg; . $_file else ( trap "echo Script $_file interrupted; kill -QUIT $$" 3 trap "echo Script $_file interrupted; exit 1" 2 set $_arg; . $_file ) fi But for '.', files in /etc/rc.d *could* be binary, but even then rcorder expects to process text files, not binary files. rcorder uses fparseln() to read each file, but this doesn't really affect reading a binary file. Thus rcorder processes binary files benignly, try 'rcorder /bin/*' and you'll see consistent output. Also in that paragraph, when I read this, ... a binary executable because rc.d can opt to feed ... ^^^^ IMHO, it should probably say, ... a binary executable because /etc/rc can opt to feed ... ^^^^^^^ though I understand you're referring to the rc.d system, some clarity is gained in that sentence by using /etc/rc. -- David __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
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