Re: Reading nth line from a file

open(FH,"test.txt");
$i=0;
$j1=0;
$j2=0;
while ( <FH> ) {

        ## If the line matches for this pattern, I should read 4th line from current line
        if ( $_ =~/you have to read the fourth line/ ){
                $j1=-4;
        }
        elsif ( $j1<0 ){
                $j1++;
                print $_ if $j1==0;
        }
        ## If the line matches for this pattern, I should read 2nd line from current line
        elsif ( $_ =~/you have to read the second line/ ){
                $j2=-2;
        }
        elsif ( $j2<0 ){
                $j2++;
                print $_ if $j2==0;
        }
print $i++,"\n";
}

Comment on Re: Reading nth line from a file

Replies are listed 'Best First'.
Re^2: Reading nth line from a file by gmontema (Initiate) on Dec 19, 2008 at 18:42 UTC
sorry disregard the previous message.	[reply]
Re^3: Reading nth line from a file by gmontema (Initiate) on Dec 22, 2008 at 23:31 UTC
open(FH,"test.txt"); my $i=0; my @p =(); while ( <FH> ) { ## If the line matches for this pattern, I should read 4th line from current line if ( $_ =~/you have to read the fourth line/ ){ push @p,$i+4; } ## If the line matches for this pattern, I should read 2nd line from current line elsif ( $_ =~/you have to read the second line/ ){ push @p,$i+2; } @p=sort(@p); foreach my $j(@p){print $_ if $j==$i; shift @p if $j<=$i;} $i++; } Input: first line 1 second line 2 third line 3 you have to read the fourth line one 5 two three 7 four five 9 six 6 you have to read the second line one 12 two three 13 first line 14 second line 15 third line 16 you have to read the fourth line you have to read the second line one 20 two with in a four four with two inside five 23 six 24 three 25 you have to read the second line you have to read the fourth line two with a for two 29 three 30 four in a two ten 32 one 33 Output: four two two with in a four four with two inside two with a for four in a two	[reply]