Date: Thu, 28 Oct 2010 10:49:03 -0700 From: Chip Camden <sterling@camdensoftware.com> To: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: [OT] writing filters in sh Message-ID: <20101028174903.GE73337@libertas.local.camdensoftware.com> In-Reply-To: <20101028192826.d3211524.freebsd@edvax.de> References: <20101027212841.GA67716@guilt.hydra> <20101028151148.GB73337@libertas.local.camdensoftware.com> <20101028160110.GA71713@guilt.hydra> <20101028161712.GC73337@libertas.local.camdensoftware.com> <20101028192826.d3211524.freebsd@edvax.de>
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[-- Attachment #1 --] Quoth Polytropon on Thursday, 28 October 2010: > On Thu, 28 Oct 2010 09:17:12 -0700, Chip Camden <sterling@camdensoftware.com> wrote: > > Perhaps someone with more sh fu can transform the > > 'if' paragraph into a one-liner at least. When I tried to do so, I got an > > unexpected ; error. > > Not tested, but this should do the trick: > > #!/bin/sh > if [ $# -ge 1 ] && ( exec cat $@ | $0; exit ) > while read data; do echo $data; done > > The ; denotes a line break, means that you can use EITHER ; or > a newline. In the original construct, > > if [ $# -ge 1 ]; then > exec cat $@ | $0 > exit > fi > > you can change the ; into > > if [ $# -ge 1 ] > then > exec cat $@ | $0 > exit > fi > > which is often seen in scripts. In this case, no ; is required (or > even allowed). The same rule applies for the while/do/done iterator. > > > -- > Polytropon > Magdeburg, Germany > Happy FreeBSD user since 4.0 > Andra moi ennepe, Mousa, ... > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" Tested, and it had a bug ('if' is extraneous). It also waits for input even if it has file arguments. But it's easily corrected: #!/bin/sh [ $# -ge 1 ] && exec cat $@ && exit | $0 while read data; do echo $data; done The first line can be converted to an alias, like so: alias inargs='[ $# -ge 1 ] && exec cat $@ && exit | $0' So, if you add the alias to your profile, you can use it to enable the behavior in any script: #!/bin/sh inargs while read data; do echo $data; done Thanks for the pointer in the right direction. -- Sterling (Chip) Camden | sterling@camdensoftware.com | 2048D/3A978E4F http://camdensoftware.com | http://chipstips.com | http://chipsquips.com [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iQEcBAEBAgAGBQJMybePAAoJEIpckszW26+RIQwH/0go9drdkfVf/VNy5zJBgq+5 aTUMV1OHhrKccffIyEoFLDAg36i31IwR+2evqvwPkGc0Vjq0RHEdmlPX75CN9RWl CKv6qdrKY8qRuLRYu66uGfJ1cFbKon71tAqAIf02iWvAa5/8b8oiskzThKWlgxlM CCPCS/fx+KNC5FsmdBDw1ySo0rCQ26M3kzjFnQBlSvIuznUDHKGIWV2Y0/nNaMII hoK6WGNCPEuTMEEf/aSUyjjdVoagXyER4UVGTW19nWq68MA2kfJLulZKcQFYIh8c Xprne3741frariUbPxhfWt9auY4aUJcQaI4yrAw5Jk9n8tx+MDeGcSv4gruIA8I= =3lXs -----END PGP SIGNATURE-----help
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