Re^2: Editing just one column in a file

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Re^3: Editing just one column in a file by BrowserUk (Patriarch) on Nov 29, 2011 at 02:35 UTC
Because the Perl syntax for an array slice is `@a[ ... ]`. If you enable warnings, you'll see that by using `$a[1..3]`, the `1..3` is treated as a flip-flop operator comparing against `$.`, and under most circumstances will produce false, which in the numeric context gets taken as 0: `c:\test>perl -wE"@a = 0..10; say $a[1..3]; say @a[1..3]" Use of uninitialized value in range (or flip) at -e line 1. Argument "" isn't numeric in array element at -e line 1. 0 123` [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re^4: Editing just one column in a file by ZWcarp (Beadle) on Nov 30, 2011 at 20:23 UTC
Why is it that this `perl -lane '$,="\t"; print @F[0..4] ."\t\t\t" . @F[25..30]' file.txt` Does not do what I intended ( for the ranges to be printed by tabs, followed by three blank columns followed by another range). Thankyou for your help!	[reply] [d/l]
Re^5: Editing just one column in a file by BrowserUk (Patriarch) on Nov 30, 2011 at 21:12 UTC
Because `$,` is the character used when you give a list of values to the print statement, but you've used '.'s. Ie. You're giving the print statement a single (concatenated) value, therefore the item separator is never used. This might achieve your goal: `perl -lane '$,="\t"; print @F[0..4], "\t\t\t", @F[25..30]' file.txt` [download] but "three blank columns" is a very nebulous concept. Update: FTR, I might code that as: `print join "\t", @F[0..4], ('')x3, @F[25..30];` [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. The start of some sanity?	[reply] [d/l] [select]
Re^4: Editing just one column in a file by vinian (Beadle) on Nov 29, 2011 at 09:00 UTC
thanks, but i got something more strange vinian@cc:~$ echo "Just another perl monker" \| perl -w -lane 'print $F +[0..3]' Argument "" isn't numeric in array element at -e line 1, <> line 1. Just vinian@cc:~$ echo "Just another perl monker" \| perl -w -lane 'print $F +[1..3]' another vinian@cc:~$ echo "Just another perl monker" \| perl -w -lane 'print $F +[2..3]' Argument "" isn't numeric in array element at -e line 1, <> line 1. Just vinian@cc:~$ echo "Just another perl monker" \| perl -w -lane 'print $F +[3..3]' Argument "" isn't numeric in array element at -e line 1, <> line 1. Just [download] when `$F[1..3]` there is no warnings and the output is `$F[1]`	[reply] [d/l] [select]
Re^5: Editing just one column in a file by choroba (Cardinal) on Nov 29, 2011 at 10:13 UTC
In scalar context, the .. operator with numeric constants is interpreted as line range. As you are reading lines with `-n` and you are on the first line, `1..3` evaluates to 1. All other ranges evaluate to undef (stringified to `''`), because the first line is out of the range, and that's why you get the warning.	[reply] [d/l] [select]
Re^5: Editing just one column in a file by Tux (Canon) on Dec 01, 2011 at 07:35 UTC
You should've used `@` again: `$ echo "Just another perl monker" \| perl -w -lane 'print @F[1..3]' anotherperlmonker $ echo "Just another perl monker" \| perl -wanE'say@F[1..3]' anotherperlmonker $ echo "Just another perl monker" \| perl -w -lane 'print @F[3..3]' monker $ echo "Just another perl monker" \| perl -wanE'say@F[3..3]' monker $` [download] Enjoy, Have FUN! H.Merijn	[reply] [d/l] [select]
Re^6: Editing just one column in a file by vinian (Beadle) on Dec 02, 2011 at 07:40 UTC


Think about Loose Coupling
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