Appending data in the start of the file

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April 24th, 2008, 01:47 AM

sridevikarthik

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Appending data in the start of the file

How to append data in the start of the file.
If i try to append using ">>" it gets appened in the last line of the file. I need my data to be appened in the first as well as in the last line of the file.
How do i do it using Perl

April 24th, 2008, 02:13 AM

kalyanraj

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Here is some idea of how to do. But this uses 2 files to do the task..

Code:

#!/usr/bin/perl -w;
open (NEWFILE, ">your new file's name") or die "Couldn't open new file: $!"; 
print NEWFILE $new_data; 
# ... and so on ... 
open (OLDFILE, "<your old file's name") or die "Couldn't open old file: $!"; 
while (chomp ($line = <OLDFILE>)) { 
    print NEWFILE "$line\n"; 
} 
close OLDFILE; 
close NEWFILE; 
# And now, if you want: rename "your new file's name", "your old file's name";

another go ... you can find some idea...

Append at the beginning

HTH
Raj

Last edited by kalyanraj : April 24th, 2008 at 02:19 AM.

April 24th, 2008, 03:52 AM

sridevikarthik

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#!/usr/bin/perl
#!/usr/bin/perl -w;
my $new_data="starting";
open (NEWFILE, ">>C:\\new.txt") or die "Couldn't open new file: $!";
print NEWFILE $new_data;

open (OLDFILE, "<C:\\old.txt") or die "Couldn't open old file: $!";
while (chomp ($line = <new.txt>)) {
print NEWFILE "$line\n";
}
close OLDFILE;
close NEWFILE;

this what i have tried...but it is not working the way what i expect..instead it gets appened only in the end and in the Start.

April 24th, 2008, 04:29 AM

kalyanraj

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I assume with your code posted that you don't have enough knowledge on Perl and simply pasting the code you've got over internet.

Please check the link in the earlier post and modify according to your requirement.

In your code:

Code:

while (chomp ($line = <new.txt>)) {

Can you tell me what exactly you're trying to do in the above...

No hard feelings please.

April 24th, 2008, 08:28 AM

vb.net

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Quote:

Try Inplace Edit or edit-in-place.

Example of the syntax from a previous post:

perl Code:

Original - perl Code
# put this in a block so that the changes to global variables don't affect other bits of my program { # load the filename into @ARGV so it can be edited in-place local @ARGV = ( $file ); # turn on in-place editing local $^I = 1; while (<>) { if ($. == 1) #-- first line of the file { #-- insert the new lines print "New line 1\n"; print "New line 2\n"; } # print the old line print; } }

# put this in a block so that the changes to global variables don't affect other bits of my program
{
    # load the filename into @ARGV so it can be edited in-place
    local @ARGV = ( $file );
 
    # turn on in-place editing
    local $^I = 1;
 
    while (<>)
    {
        if ($. == 1)    #-- first line of the file
        {
            #-- insert the new lines
            print "New line 1\n";
            print "New line 2\n";
        }
 
        # print the old line
        print;
    }
}

April 25th, 2008, 02:13 AM

KevinADC

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expanding on vb.nets code, which is also the way I would do it:

Code:

# put this in a block so that the changes to global variables don't affect other bits of my program
{
    # load the filename into @ARGV so it can be edited in-place
    local @ARGV = ( "file.txt" );

    # turn on in-place editing
    local $^I = '.bac';

    while (<>)	{
        print "New Line\n" if $. == 1;
        if (eof) { # add the new line to the end also
            print;
            print "\nNew Line\n";
        }
        else {
            print;
        }
    }
}

Note the double newlines here:

Code:

print "\nNew Line\n";

If you know the last line of the file has a newline on the end you can drop the first newline.

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