Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Combine multiple images into a single image with ImageMagick
Answer:
With the powerful ImageMagick program, we can easily handle common graphics tasks using command only.
For example, to combine multiple images into a single image, we need just one command:
# convert file1.jpg file2.jpg file3.jpg +append -quality 90 'output.jpg'
The above command (file1.jpg file2.jpg file3.jpg) into the file output.jpg with quality set to 90.
Show the current user in MySQL
Answer:
Like in the shell, we can execute the command whoami to find out the current user name, we can use the function CURRENT_USER();
E.g.
mysql> SELECT CURRENT_USER();
+----------------+
| CURRENT_USER() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)Install NodeJS in Linux
Answer:
In order to install NodeJS in Linux, the recommended way is compile from source and install it.
# wget http://nodejs.org/dist/node-v0.4.11.tar.gz
# tar zxf node-v0.4.11.tar.gz
# cd node-v0.4.11
# ./configure
# sudo make && make installNow you can type node to enter the node's REPL
How to remove object from array inside foreach loop?
Answer:
In PHP, to remove object (e.g. with the key = foo in the following example) from array inside foreach loop, you can try:
<?php
foreach($array as $key=> $value) {
if ($key == "foo") {
unset($array[$key]);
}
}Remove all queued message in Postfix
Answer:
To remove queued message in your Postfix server, you should always check the queue listing first.
When you have confirmed, then you can do
1. Remove specific message based on Queue ID (You can find the ID via postqueue command)
# sudo postsuper -d Queue_ID
2. Remove all messages
# sudo postsuper -d ALL
