pvighneshmufc:

He meant that the following lines are inside of a loop, like this:

# read file1 into a %hash
... code to do that here ...

# inside a loop
while (my $line = <$file2>) {
    # read file2 line by line
    ... this was done in the loop condition above ...

    # split the $line to @fields at |

    # if the first $fields[0] exists in the %hash,
        # print the whole $line to file 3
}
[download]

This is a relatively common question, so LanX gave you the outline of a good solution to the problem.

A frequent mistake is to try to read *both* files inside the loop, giving one of two bad outcomes:

• Either the first file is completely read in the first pass of the loop, so the code can only find a single match if it happens to be the first line in the second file, or
• the code re-opens the first file each time, and therefore can find all the matches, but runs extremely slowly⁽¹⁾ because it reads the first file completely for each line in the second file.

(1) Extremely slowly in the relative sense--for small files you may not notice it. But if your files get large enough, you'll wonder why such a fast computer is so freakin' slow.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

The file has around 7 lakh lines so yeah :p

If your File1 has 700,000 lines, rest assured that a hash can easily accommodate this number of lines or even many more — if the lines are sufficiently short, i.e., not thousands of characters!

One pitfall to avoid: When you read each line from your File1, it will have some kind of line-end delimiter, typically a newline. This will have to be removed (see chomp) before adding it to the lookup hash because a COA213345 field split from the beginning of a line in File2 will have no such delimiter. (Looking up a key in a hash (see exists) is essentially an  eq string exact equality operation.)

Perhaps take a look at some of the articles in the Input and Output section of the Monastery's Tutorials.

---

Give a man a fish:  <%-{-{-{-<

Lakh is not really a standard English word!

Maybe you should show some efforts in programing AND your communication skills?

So yeah :p

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Wikisyntax for the Monastery}

PS: We are still happy to help you fixing code, as soon as you show some.

http://perlmaven.com/open-and-read-from-files

The first code example shows it already, though $line is named $row here.

I'm not going to give you complete code, because I want to help you to learn Perl. :)

Thanks a lot , suggest me some tutorials to start with , i am very new to this so suggest like that :p

There's the tutorials section of this site to start with.

See Files and I/O in perlintro.