Date: Fri, 29 Mar 2019 09:36:02 -0400 From: Paul Mather <freebsd-lists@gromit.dlib.vt.edu> To: freebsd-questions@freebsd.org Cc: Polytropon <freebsd@edvax.de>, Michael Sierchio <kudzu@tenebras.com>, mayuresh@kathe.in Subject: Re: Sending Tcsh to packages/ports ... Message-ID: <0CE431C9-683E-423F-A0A5-D06C3363C411@gromit.dlib.vt.edu> In-Reply-To: <mailman.5940.1553830572.52788.freebsd-questions@freebsd.org> References: <mailman.5940.1553830572.52788.freebsd-questions@freebsd.org>
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> Date: Fri, 29 Mar 2019 03:56:38 +0100 > From: Polytropon <freebsd@edvax.de> > To: Michael Sierchio <kudzu@tenebras.com> > Cc: mayuresh@kathe.in, FreeBSD Questions > <freebsd-questions@freebsd.org> > Subject: Re: Sending Tcsh to packages/ports ... > Message-ID: <20190329035638.db780898.freebsd@edvax.de> > Content-Type: text/plain; charset=3DUS-ASCII >=20 > On Thu, 28 Mar 2019 19:03:24 -0700, Michael Sierchio wrote: >> *kudzu@hearst:/bin 130>* ll -i | grep csh >>=20 >> 198147 -r-xr-xr-x 2 root wheel 427888 Jun 22 2018 csh* >>=20 >> 198147 -r-xr-xr-x 2 root wheel 427888 Jun 22 2018 tcsh* >>=20 >=20 > The csh / tcsh is not the only system component known by > more than one name: >=20 > % hardlinks.sh /bin > 23621: csh tcsh <--- ! > 23627: ed red=20 > 23633: link ln=20 > 23638: pgrep pkill=20 > 23644: rm unlink=20 > 24944: [ test >=20 > It's important to note that by querying $0 or argv[0], a > program can change its behaviour depending on the way it > has been invoked. So a call to "csh" could cause the program > to do things differently than if it was called by "tcsh". >=20 > Of course this also applies to _any_ programs, being part > of the OS or being installed by ports. Indeed, this is the mechanism by which the /rescue system works: lots of = hard links to a statically-linked /rescue/rescue binary, which behaves = differently depending upon with which program name it's being invoked. = In the case of /rescue this saves a lot of space over having separate = static binaries. Cheers, Paul.
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