One-liner only checking the first line of the input file

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

I have an 8-column input tab-delimited .txt file and wish to print the contents of column 3 + 8 when the value held within column 8 is >0.

I've tried:

perl -lane 'print "$F[2]\t$F[7]" if $F[7] > 0' < input.txt

However this only returns a single line (the first line) when there are multiple matching lines. I want it to iterate over every line instead. What have I done wrong?

For example, if my input file contains:

77 * 10 0 * * 0 340

141 * 40 0 * * 0 240

The output file will only contain:

10 340

Comment on One-liner only checking the first line of the input file Select or Download Code

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Re: One-liner only checking the first line of the input file by stevieb (Canon) on Nov 11, 2015 at 14:23 UTC
Are your line endings what you expect (ie. is the file being treated as one long line as opposed to several)? Try this, and see if you get a single line, or all of the lines printed: `perl -lane 'print $_; exit;' input.txt` [download]	[reply] [d/l]
Re^2: One-liner only checking the first line of the input file by TJCooper (Beadle) on Nov 11, 2015 at 14:30 UTC
`perl -lane 'print $_; exit;' input.txt > output.txt` Output.txt appears identical to the input file - all lines are printed.	[reply] [d/l]
Re^3: One-liner only checking the first line of the input file by stevieb (Canon) on Nov 11, 2015 at 14:41 UTC
Do this: `perl -anE '/(\R)/; say unpack("H", $1);' input.txt` [download] It appears as your file is being read as one long string. If you're on nix, your output should be `0a` per line for as many lines you have in the file. Post what the output shows.	[reply] [d/l] [select]
Re^4: One-liner only checking the first line of the input file by TJCooper (Beadle) on Nov 11, 2015 at 14:51 UTC
Re^5: One-liner only checking the first line of the input file by stevieb (Canon) on Nov 11, 2015 at 15:04 UTC
Some notes below your chosen depth have not been shown here
Re: One-liner only checking the first line of the input file by GotToBTru (Prior) on Nov 11, 2015 at 14:44 UTC
I copied your code and data verbatim and it works for me. `howard$: cat input.txt 77 * 10 0 * * 0 340 141 * 40 0 * * 0 240 howard$: perl -lane 'print "$F[2]\t$F[7]" if $F[7] > 0' < input.txt 10 340 40 240` [download] Environment is AIX, Perl 5.8.8. Dum Spiro Spero	[reply] [d/l]
Re: One-liner only checking the first line of the input file by Laurent_R (Canon) on Nov 11, 2015 at 15:07 UTC
Since your code and data seem to be working under Unix, are you perhaps working under Windows (or old Mac) with a file prepared with an Unix format? Under which OS are your working?	[reply]
Re^2: One-liner only checking the first line of the input file by TJCooper (Beadle) on Nov 11, 2015 at 15:14 UTC
OS X (10.11.2) This is perl 5, version 18, subversion 2 (v5.18.2) built for darwin-thread-multi-2level (with 2 registered patches, see perl -V for more detail) File was prepared on the same system.	[reply]
Re: One-liner only checking the first line of the input file by hippo (Bishop) on Nov 11, 2015 at 14:39 UTC
Your code and data as given work for me. The output (on perl v5.20.3) is: `10 340 40 240` [download] Are you sure your data set is what you think it is? Does adding `-w` to the options do you any good?	[reply] [d/l] [select]
Re^2: One-liner only checking the first line of the input file by TJCooper (Beadle) on Nov 11, 2015 at 14:44 UTC
Including `-w` produces the same result. I've uploaded a small sample of my .txt file here: https://www.dropbox.com/s/jelbmyf7nzn3n70/READS.txt?dl=0	[reply] [d/l]
Re^3: One-liner only checking the first line of the input file by hippo (Bishop) on Nov 11, 2015 at 15:05 UTC
Thanks for that. I don't use dropbox so have no concept of how (or not) they might have munged that. Instead, here are some hashes of my input.txt which works: SHA256: e49d0b5631cfdf9de7bc4571716e368c5fbfb394d9f224caa7c63c7608c55b77 SHA1: 343eca42bb1e78dbf69eb3c2736afb65ab680dce MD5: afe5fb04f8d6edcf57a04eb3ced196ef Compare one of those with the hash of your source and see if/how it differs. I'm using unix EOLs and am including the blank line in the middle.	[reply]

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