60 posts tagged with "tips"

Natively, Linux has a command-line tool called diff for comparing two folders or files. Comparing two folders is quite simple: diff folder_1 folder2. And it's no more complicated for two files: diff file_1 file2.

However, when you want to do this in a slightly more industrialised way (launch a very large number of comparisons to compare two versions of the same project, for example), the use of a few flags and snippets comes in handy.

When faced with legacy code, it is often useful to reformat it to make it readable. And from there, the study of the code can begin.

There are plenty of reformatting tools for json, php, javascript and other languages, but far fewer for a query written in SQL.

Just copy/paste SELECT LAT_N, CITY, TEMP_F FROM STATS, STATION WHERE MONTH = 7 AND STATS.ID = STATION.ID ORDER BY TEMP_F in the tool and get

SELECT
    LAT_N,
    CITY,
    TEMP_F
FROM
    STATS,
    STATION
WHERE
    MONTH = 7
    AND STATS.ID = STATION.ID
ORDER BY
    TEMP_F

When I'm learning, I usually take notes. I find that it's one of the best ways of remembering what I've seen and being able to come back to it at any time.

Below is a note that I took and revised several times when I took the time to create my first .make files.

A concept of the clean code approach is to avoid too many function parameter (I would say that four parameters is already too many).

When you're programming in a language more advanced than Linux Bash, it's easy to get round the problem. For example, in PHP, if I need to call a function and pass it several parameters, I'll create an object that will be my only parameter and that object will then have several properties.

So, for instance, if I need to pass data such as a surname, first name, date of birth, gender, etc., I'll create a person object, define my properties and voilà, I've only got one parameter to pass to my function. In most cases, it'll be a very nice solution.

But how do you do it in Linux Bash? It's impossible to pass an object... so I'm going to pass it an associative array.

Because you're an excellent developer, you deny anyone access to the properties of your class directly, but only via a getter or setter.

In other words, in your PHP class, you don't have public properties (they're devil) but exclusively protected ones or better private.

And using getter and setters you allow other objects to interact with your private methods by reading them (getters) or updating their values (setters).

Some people will say "Yes, but it's tedious to write these functions", but not at all.

Imagine you to have a very big docker-compose.yml file with a lot of services and dependencies.

You've too multiple exposed ports.

You'd like to have an at-a-glance view of services, dependencies and open ports. Is this possible? Yes! https://github.com/compose-viz/compose-viz do the magic for us.

A long time ago, years from now, I needed to expose data from my Joomla site in a simple web page outside Joomla, as an HTML table. This was so that I could link a Microsoft Excel spreadsheet to this table and therefore, in Excel, simply do a Refresh to obtain the most recent data from my Joomla site.

The aim was to find the list of people who had bought software or services from me. Among other things, I needed their first name, family name, billing address, etc. so that I could create an invoice in Microsoft Word using the mail merge functionality (data source=Excel).

Of course, just running a query on your database and show the result as a web page can be really useful.

Have you ever deleted a website from your FTP client? It's easy, just select the folder containing the website and press the delete key.

Easy, simple and ... so slow. It takes ages to suppress files / folders. Several dozen minutes! Ouch.

If you've a SSH connection to your web server and if you're comfortable with it; you can rm -rf the folder and it'll be done in seconds.

But what if you don't have SSH or fear to make errors?

There is an alternative, the erase.php script.

By the use of a script, it's possible to ask WinSCP to synchronize your host and remote machine i.e. if a file is newer on the host, copy it to your remote server and the opposite.

If a file has been added to your host, copy it to your remote server and vice versa.

I'm using such script for making a full backup of some of my folders to my Synology.

In my previous article Bash - Script to add logging features to your script, I've shared a way to write information in a logfile.

By running ls -alh /tmp you will get the list of all files in the /tmp folder and display the list on your console. By running ls -alh /tmp >> application.log you won't see the list in your console since everything will be written in the application.log file.

How can we display the output of a command like ls f.i. both on the console and in a logfile?