To update one file with the another file"s data..

Hi,

I have two text files: each one has has four fields (delimited by a
space) on each line: id, group, email and manager_id. First file is a
small file with 50 entries and the second one is a huge file with
5,000 entries. The "id" field is same in both files, but the
manager_id's may be different. By comparing all the entries in the
second file (that has the correct manager id), I need to update the
manager_id field in the first file.

Here is the code, I am thinking of:

-----------------------------------------
open (INPUT1,"smallFile.txt") or die "Cannot open the file: $!";
open (INPUT2,"bigFile.txt") or die "Cannot open the file: $!";


while $line1 ()
{
@small_arr = split /\s+/, $line1;
}

while $line2 ()
{
@big_arr = split /\s+/, $line2;
}


foreach (@small_arr)
{
if ($small_arr[0] == $big_arr[0] ) # first ID is same in both
files
{
$small_arr[3] = $big_arr[3];
print "$_\n";
}
}

-------------------------------------------------

I know some thing is certainly wrong here. can some one tell me pl.?

Thanks,
J

Re: To update one file with the another file"s data..

On Jan 17, 12:35 pm, cleargu...@yahoo.com wrote:
> while $line1 ()
> {
> @small_arr = split /\s+/, $line1;
> }

You are reading the entire file and assigning the fields of each line
to an array. But the array only holds the fields of a single line.
By the time the while loop is done, the array holds only the fields
for the last line of the file. You have thrown away all the rest of
the file. Same thing for your second loop. That's the main reason
why your program doesn't work.

I would approach it by building a hash of the id/manager values from
the big file and then running through the second file to make the
corrections. Here's an example suitable for a newsgroup posting which
uses a DATA block for the big file and a hardcoded array for the small
file. In reality these would both be files, and you would read the
second file one-line-at-a-time with a while loop.

#!/usr/bin/perl
use strict; use warnings;

my @small = (
"id2 group1 email1 WRONG1",
"id3 group3 email3 mgr3",
"id5 group5 email5 WRONG2",
);

my %big_file_mgr;
while () {
my ($id, $mgr) = (split(/\s+/, $_))[0,3];
$big_file_mgr{$id} = $mgr;
}

foreach (@small) { #this would be: while () {
my ($id, $group, $email, $mgr) = (split(/\s+/, $_));
$mgr = $big_file_mgr{$id} if $big_file_mgr{$id};
print "$id $group $email $mgr\n";
}

__DATA__
id1 group1 email1 mgr1
id2 group2 email2 mgr2
id3 group3 email3 mgr3
id4 group4 email4 mgr4
id5 group5 email5 mgr5

--
The best way to get a good answer is to ask a good question.
David Filmer (http://DavidFilmer.com)