read certain lines in a file

[unclescrooge]

Hi

I need some help, I have created a file with a perl script with contents in it how do I print each and every second line out of the file?

Thanks

 

[KevinADC]

please post the code you have so far. Or look into using the $. variable (input record line number) and the modulus '%' operator, or using Tie::File (or reading the file into an array: not recommended for really big files), and some initialization condition:

[black][b]for[/b][/black] [red]([/red][black][b]my[/b][/black] [blue]$i[/blue] [black]=[/black] [fuchsia]0[/fuchsia][black],[/black] [blue]$i[/blue] [black]<[/black] [blue]@array[/blue][black],[/black] [blue]$i[/blue][black]+=[/black][fuchsia]2[/fuchsia][red])[/red][gray][i]#for even numbers[/i][/gray]
   [black][b]print[/b][/black] [red]"[/red][purple][blue]$array[/blue][[blue]$i[/blue]][purple][b]\n[/b][/purple][/purple][red]"[/red][red];[/red]
[red]}[/red]

[black][b]for[/b][/black] [red]([/red][black][b]my[/b][/black] [blue]$i[/blue] [black]=[/black] [fuchsia]1[/fuchsia][black],[/black] [blue]$i[/blue] [black]<[/black] [blue]@array[/blue][black],[/black] [blue]$i[/blue][black]+=[/black][fuchsia]2[/fuchsia][red])[/red][gray][i]#for odd numbers[/i][/gray]
   [black][b]print[/b][/black] [red]"[/red][purple][blue]$array[/blue][[blue]$i[/blue]][purple][b]\n[/b][/purple][/purple][red]"[/red][red];[/red]
[red]}[/red]

- Kevin, perl coder unexceptional!

 

[unclescrooge]

Hi

My code is as follows:

open OUTPUT,">text.txt";

for (@list)
{
print OUTPUT ( (split)[3, 8], "\n")

}
close OUTPUT;

open INPUT,"<text.txt";

@list=<INPUT>;

close INPUT;


print "Every second line is:\n";
for ($list = 0, $list < @list, $list+=2)
{
print "@list[$list]\n";

}

 

[KevinADC]

I'm sorry, my code was not correct. In the initialization part the commas should be semi-colons:

for ($list = 0[red];[/red] $list < @list[red];[/red] $list+=2)

- Kevin, perl coder unexceptional!

 

[unclescrooge]

Thanks so much it worked great

 

[unclescrooge]

Hi

If you look at my code where I did the second loop to print certain lines. That works great but now my text file is open how do I re-write or safe the changes into the text file as print OUTPUT .. is not working

 

[KevinADC]

I don't understand your question.

- Kevin, perl coder unexceptional!

 

[Mike042]

If you look at my code where I did the second loop to print certain lines. That works great but now my text file is open how do I re-write or safe the changes into the text file as print OUTPUT .. is not working

At that point in your code OUTPUT is closed and INPUT is closed!
To re-write to your text file, open it again.
NB if you use:
open OUTPUT, ">text.txt";
it will overwrite text.txt
If you use
open OUTPUT, ">>text.txt";
it will append to the end of the file.


I hope that helps.

Mike