Databases
StackOverflow2013
Postsdbo
POHow to sort rows in a text file in Perl?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow to sort rows in a text file in Perl?
    primarykey
    data
    text
    <p>I have a couple of text files (<code>A.txt</code> and <code>B.txt</code>) which look like this (might have ~10000 rows each)</p> <pre><code>processa,id1=123,id2=5321 processa,id1=432,id2=3721 processa,id1=3,id2=521 processb,id1=9822,id2=521 processa,id1=213,id2=1 processc,id1=822,id2=521 </code></pre> <p>I need to check if every row in file <code>A.txt</code> is present in <code>B.txt</code> as well (<code>B.txt</code> might have more too, that is okay).</p> <p>The thing is that rows can be in any order in the two files, so I am thinking I will sort them in some particular order in both the files in <code>O(nlogn)</code> and then match each line in <code>A.txt</code> to the next lines in <code>B.txt</code> in <code>O(n)</code>. I could implement a hash, but the files are big and this comparison happens only once after which these files are regenerated, so I don't think that is a good idea.</p> <p><strong>What is the best way to sort the files in Perl?</strong> Any ordering would do, it just needs to be <em>some</em> ordering.</p> <p>For example, in dictionary ordering, this would be</p> <pre><code>processa,id1=123,id2=5321 processa,id1=213,id2=1 processa,id1=3,id2=521 processa,id1=432,id2=3721 processb,id1=9822,id2=521 processc,id1=822,id2=521 </code></pre> <p>As I mentioned before, any ordering would be just as fine, as long as Perl is fast in doing it.</p> <p>I want to do it from within Perl code, after opening the file like so</p> <pre><code>open (FH, "&lt;A.txt"); </code></pre> <p>Any comments, ideas etc would be helpful.</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USLazer
    1. USLazer
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow to sort rows in a text file in Perl?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow to sort rows in a text file in Perl?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POHow to sort rows in a text file in Perl?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COIf you're doing 10,000 rows, and you're planning on using this more than once -- at the least I'd be using SQL Lite.
      singulars
      1. POHow to sort rows in a text file in Perl?
      1. USEvan Carroll
    2. COA hash and a sort both require you to load the entire `A.txt` file into memory. Why do you think sorting is better than using a hash?
      singulars
      1. POHow to sort rows in a text file in Perl?
      1. USmob
    3. CO@mobrule: I thought that Perl might have some intelligent way of sorting it, given that it is a language that is built for dealing with text. Some way that is better than implementing a hash myself. From the answers below, it seems that hashing is after all a good idea!
      singulars
      1. POHow to sort rows in a text file in Perl?
      1. USLazer
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload