variable substitution into awk commands
in [Shell]
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From: banzai on 17 Nov 2006 12:09 Have a file $SCRATCH, print lines 1 to 2: $ awk 'NR==1,NR==2' ${SCRATCH} 20061104 0000 0000035901 20061104 0005 0000040269 If I want to assign variables to 1 & 2 above it doesn't parse $ FROM=1 $ TO=2 $ awk 'NR==${FROM},NR==${TO}' $SCRATCH awk: cmd. line:1: NR==${FROM},NR==${TO} awk: cmd. line:1: ^ parse error awk: cmd. line:1: NR==${FROM},NR==${TO} awk: cmd. line:1: ^ parse error awk: cmd. line:1: NR==${FROM},NR==${TO} awk: cmd. line:1: ^ parse error $ Can this be escaped - Any ideas ? Thks
From: Barry Margolin on 17 Nov 2006 12:01 In article <D1m7h.2672$LK5.1239(a)news.cpqcorp.net>, "banzai" <banzai(a)aa.com> wrote: > Have a file $SCRATCH, print lines 1 to 2: > > $ awk 'NR==1,NR==2' ${SCRATCH} > 20061104 0000 0000035901 > 20061104 0005 0000040269 > > If I want to assign variables to 1 & 2 above it doesn't parse > > $ FROM=1 > $ TO=2 > $ awk 'NR==${FROM},NR==${TO}' $SCRATCH > awk: cmd. line:1: NR==${FROM},NR==${TO} > awk: cmd. line:1: ^ parse error > awk: cmd. line:1: NR==${FROM},NR==${TO} > awk: cmd. line:1: ^ parse error > awk: cmd. line:1: NR==${FROM},NR==${TO} > awk: cmd. line:1: ^ parse error > $ > > Can this be escaped - Any ideas ? > Thks Variables are expanded inside double quotes, but nott inside single quotes. awk "$FROM,$TO" $SCRATCH Although awk seems to be a bit of overkill for this, I'd use sed -n "${FROM},${TO}p" $SCRATCH -- Barry Margolin, barmar(a)alum.mit.edu Arlington, MA *** PLEASE post questions in newsgroups, not directly to me *** *** PLEASE don't copy me on replies, I'll read them in the group ***
From: banzai on 17 Nov 2006 12:41 "Barry Margolin" <barmar(a)alum.mit.edu> wrote in message news:barmar-35E971.12013017112006(a)comcast.dca.giganews.com... > In article <D1m7h.2672$LK5.1239(a)news.cpqcorp.net>, > "banzai" <banzai(a)aa.com> wrote: > >> Have a file $SCRATCH, print lines 1 to 2: >> >> $ awk 'NR==1,NR==2' ${SCRATCH} >> 20061104 0000 0000035901 >> 20061104 0005 0000040269 >> >> If I want to assign variables to 1 & 2 above it doesn't parse >> >> $ FROM=1 >> $ TO=2 >> $ awk 'NR==${FROM},NR==${TO}' $SCRATCH >> awk: cmd. line:1: NR==${FROM},NR==${TO} >> awk: cmd. line:1: ^ parse error >> awk: cmd. line:1: NR==${FROM},NR==${TO} >> awk: cmd. line:1: ^ parse error >> awk: cmd. line:1: NR==${FROM},NR==${TO} >> awk: cmd. line:1: ^ parse error >> $ >> >> Can this be escaped - Any ideas ? >> Thks > > Variables are expanded inside double quotes, but nott inside single > quotes. > > awk "$FROM,$TO" $SCRATCH > > Although awk seems to be a bit of overkill for this, I'd use > > sed -n "${FROM},${TO}p" $SCRATCH > > -- > Barry Margolin, barmar(a)alum.mit.edu > Arlington, MA > *** PLEASE post questions in newsgroups, not directly to me *** > *** PLEASE don't copy me on replies, I'll read them in the group *** yep, thanks
From: Ed Morton on 18 Nov 2006 00:32 banzai wrote: > "Barry Margolin" <barmar(a)alum.mit.edu> wrote in message > news:barmar-35E971.12013017112006(a)comcast.dca.giganews.com... > >>In article <D1m7h.2672$LK5.1239(a)news.cpqcorp.net>, >>"banzai" <banzai(a)aa.com> wrote: >> >> >>>Have a file $SCRATCH, print lines 1 to 2: >>> >>>$ awk 'NR==1,NR==2' ${SCRATCH} >>>20061104 0000 0000035901 >>>20061104 0005 0000040269 >>> >>>If I want to assign variables to 1 & 2 above it doesn't parse >>> >>>$ FROM=1 >>>$ TO=2 >>>$ awk 'NR==${FROM},NR==${TO}' $SCRATCH >>>awk: cmd. line:1: NR==${FROM},NR==${TO} >>>awk: cmd. line:1: ^ parse error >>>awk: cmd. line:1: NR==${FROM},NR==${TO} >>>awk: cmd. line:1: ^ parse error >>>awk: cmd. line:1: NR==${FROM},NR==${TO} >>>awk: cmd. line:1: ^ parse error >>>$ >>> >>>Can this be escaped - Any ideas ? >>>Thks >> >>Variables are expanded inside double quotes, but nott inside single >>quotes. >> >>awk "$FROM,$TO" $SCRATCH >> <snip> > yep, thanks > To be safe and efficient: awk -v from="$FROM" -v to="$TO" 'NR>to{exit}NR>=from' "$SCRATCH" See question 24 in the FAQ (http://home.comcast.net/~j.p.h/cus-faq-2.html#24). Ed.
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