Wish to keep only those lines which start with letter s, and delete all other lines.

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Wish to keep only those lines which start with letter s, and delete all other lines. by Beatnik (Parson) on Dec 06, 2001 at 03:42 UTC
`perl -pi.bak -e'if (!/^s/) { $_ = "" }' filename` in shell Greetz Beatnik ... Quidquid perl dictum sit, altum viditur.	[reply] [d/l]
Re: Wish to keep only those lines which start with letter s, and delete all other lines. by Fastolfe (Vicar) on Dec 06, 2001 at 03:47 UTC
If you're on Unix, you don't necessarily need Perl for this at all: `$ egrep -v ^s input-file` [download]	[reply] [d/l]
Re: Wish to keep only those lines which start with letter s, and delete all other lines. by Chmrr (Vicar) on Dec 06, 2001 at 04:10 UTC
Another varient on the `-pi.bak -e` ("pi bake") schemata, but using the powers of the "ni bake": `perl -ni.bak -e'print if /^s/'` perl -pe '"I lo`+$^X$\"$]!$/"=~m%(.)%s;$_=$1;y^+*`^ ve^#$&V"+@( NO CARRIER'	[reply] [d/l] [select]
Re: Wish to keep only those lines which start with letter s, and delete all other lines. by wog (Curate) on Dec 06, 2001 at 04:27 UTC
Golfing a bit: `perl -i -ne'/^s/i..print' # or if we don't care about capital s... perl -i -ne'/^s/..print'` [download] update: `s/-ine/-i -ne/g # stupid mistake`	[reply] [d/l] [select]
Re: Re: Wish to keep only those lines which start with letter s, and delete all other lines. by blakem (Monsignor) on Dec 06, 2001 at 06:01 UTC
Did someone say golf? ;-) `perl -i -pe'$_ x=/^s/i'` [download] -Blake	[reply] [d/l]
Re: Wish to keep only those lines which start with letter s, and delete all other lines. by lestrrat (Deacon) on Dec 06, 2001 at 03:46 UTC
caution: the following code does an in-place edit. make sure to back up ( well, the -i.bak does it for you, but it can't hurt to be careful ) `perl -i.bak -pe 's/^[^s].*\z//' file`	[reply] [d/l]
Re: Wish to keep only those lines which start with letter s, and delete all other lines. by vek (Prior) on Dec 06, 2001 at 06:00 UTC
`substr` anyone? Assuming file already opened successfully... `while ( <THEFILE> ) { next if ( substr ( $_, 0, 1 ) =~ /s/i ); # now do stuff with the lines you do want }` [download]	[reply] [d/l] [select]
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