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In Linux you can use split and join commands to split large files into smaller files or join many smaller files into a large file. This kind of operations are often necessary when you are dealing with large quantities of data.

split

Following is the default functionality of split. It splits a large file every thousand lines and creates new files.

$ split largefile.txt

$ ls
largefile.txt  xaa xab  xac  xad

$ wc -l *
3285  largefile.txt
1000  xaa
1000  xab
1000  xac

You can also define the number of lines you want in each file

The Following SQL query will list all tables in a MySQL database and also list the row counts for each.

SELECT TABLE_NAME, TABLE_ROWS 
FROM `information_schema`.`tables` 
WHERE `table_schema` = 'mydatabase';

where mydatabase is the name or your database. The output will like something like the following:

+------------+------------+
| table_name | table_rows |
+------------+------------+
| lines      |       2271 |
| links      |        484 |
| word       |      25004 |
+------------+------------+

If you have installed MySQL on your Mac and forgot your root password, these instructions are for you.

The following code read the contents of a text file

#!/bin/bash
filename='links.txt'
while read -r line
do
    echo $line
done <"$filename"

To read first five lines only

head -5 dinks.txt | while read a; do
    echo $a;
done

Read five lines and then delete those lines

head -5 links.txt | while read a; do
    echo $a;
done
sed -i "1,5 d" links.txt

Following code uses DOM to extract links.

Perl string literals are enclosed in quotation marks. You can use either single quotes ('') or double quotes ("").

print "hello";
print 'hello'; 

Now suppose you need to print a string which contains a single or double quote such as following strings:

This is bob's watch.
Alice replied, "It was a birthday gift."

If I do the following,

Problem

You pushed your changes to GIT but you don't see it in the repository.

Diagnosis

First thing is to compare status with log

git log

will give you a list of the commits. You will not see your changes here.

git status

You will see your files here. Above the list of files, you will see

Changes to be committed

Cause

The reason you don't see your changes in repository is because they were not committed.

If a string contains a single quote, it will generate an error. mysqli->real_escape_string() escapes quotes for MySQL. See example:

Replace multiple spaces with one space

See the following code:

<?php
  $str = 'This    string    has   many   spaces';
  $str = preg_replace('/\s+/', ' ', $str);
  print $str;
?>

output

This string has many spaces

Epoch time is Unix timestamp which counts the number of seconds since January 1 1970 00:00:00 UTC. Without getting into long discussion, follow is how your convert between human readable date and epoch time.

Convert Human Readable Date to Epoch Time

<?php
  $now = strtotime('2010-04-25');
  print $now;
?>

Convert Epoch Time to Human Readable Time

<?php
  $human_date=date("Y-m-d", 1251627495);
  print human_date;
?>