Saturday, October 27, 2018

Net::HTTP error sending GET request with parameters

If you're getting trouble with Net::HTTP#send_request when sending a GET request with parameters, one possible cause is that parameters must be part of path as a query string, and not as data (3rd parameter of #send_request).

For example (assuming that parameters is not empty), instead of

http = Net::HTTP.new('server.com')
http.send_request('GET', path, parameters, headers)

try:

http = Net::HTTP.new('server.com')
http.send_request('GET', path + '?' + parameters, '', headers)

Net::HTTP error 400 (bad request) with HTTPS

Hello, friends!

Yesterday I got stuck when trying to connect to an HTTPS site using Net::HTTP:

      http = Net::HTTP.new('server.com', 443)
      response = http.send_request('GET', path, parameters, headers)

I was getting error 400 in response.code.

What is not well documented is that when accessing a server via HTTPS protocol it's not enough to set port to 443. You must also set use_ssl to true:

      http = Net::HTTP.new('server.com', 443)
      http.use_ssl = true
      response = http.send_request('GET', path, parameters, headers)


Tuesday, March 21, 2017

Pipe inside a bash script

Hello!

Today I got stuck trying to use pipe inside a command variable in a bash script:

$CMD="echo foo | cat"
EXEC=`$CMD`                 # expecting foo
echo $EXEC                  # got foo | cat


I could solve that if I run the command directly, without variables:

EXEC=`echo foo | cat`       # expecting foo
echo $EXEC                  # got foo


But that was not an option, because $CMD was complex and carefully mounted before that snippet.

Googling around I found that the solution is to use eval (although I used it slightly different from the source):

$CMD="echo foo | cat"
EXEC=`eval $CMD`            # expecting foo
echo $EXEC                  # got foo


The reason is that eval can expand the pipe command inside a variable, while backticks can't.

Cheers!

Wednesday, August 31, 2016

How to install mysql2 gem on Ubuntu

If you are having trouble to install the mysql2 gem, try the following:

# apt-get install build-essential ruby-dev libmysqlclient-dev

Sunday, July 24, 2016

Slides: Introduction to Ruby

I'm here today to share a presentation that I've made to a group of Software Development students.

Click here to see the presentation.

I'm sorry for a piece of code that was not translated (variable names in portuguese), but I think that you can get the idea (comparing how PHP is spelling and how Ruby is expressive).

Monday, April 21, 2014

Installing Ruby 2.1.1 in Ubuntu 14.04

The apt-get way don't install the latest stable Ruby (2.1.1), even on Ubuntu 14.04. Instead, I got 1.9.3 that way. RVM can be easy, but to work with Apache I'd need a system-wide installation independent of the RVM environment. So I've decided to install Ruby from source. I had problems around readline, but after seeing this hint, the solution that worked for me is:

./configure --with-readline-dir=/usr/lib/x86_64-linux-gnu/libreadline.so
make
make install

on the directory of the unpacked source of Ruby 2.1.1, as root. I suspect there is a more elegant solution out there, but this is enough for me at this time.

Friday, March 7, 2014

LOAD DATA INFILE tips

If you're having troubles with LOAD DATA INFILE ("Errcode 13"):
  • copy the CSV file to the DB folder (/var/lib/mysql/DATABASE), and
  • use the filename only, not the full path.


If you're having troubles with LOAD DATA LOCAL INFILE ("The used command is not allowed with this MySQL version"):
  • temporary solution: mysql -uUSER -p --local-infile DATABASE
  • permanent solution: sudo nano /etc/mysql/my.cnf and insert local-infile under [mysql]; save the file, close the editor and type sudo service mysql restart.

Note: LOAD DATA LOCAL INFILE uses IGNORE. If you want to know why some records were skipped, you must use LOAD DATA INFILE (without LOCAL). (Reference)