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 current Postfix queue listing
Answer:
To show the current Postfix queue, you can try the command "postqueue"
# postqueue -p
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
BD7E2BF973 972 Sat Aug 27 08:57:54 no-reply@example.com
(connect to alt4.gmail-smtp-in.l.google.com[209.85.143.27]:25: Connection timed out)
johndoe@gmail.com
Post a file to a server using the Curl command
Answer:
You can simulate a HTTP form post, with a file being uploaded to a remote server using the curl command.
curl -F 'photo=@/upload/image.jpg' http://example.com/upload.phpAssume the name of the form element of your upload is called "photo"
Debug and verify Postfix configurations
Answer:
A simple way to debug and verify your Postfix configurations is the use the sendmail command with the -bv flag.
Example:
# sendmail -bv username@example.com
No email will be sent using the above command, it just report after verifying each recipient address. This is very useful for testing the Postfix configurations.
Create a transparent image using ImageMagick
Answer:
You can use the following command to create an empty png file, using the ImageMagick.
# convert -size 100x100 xc:none empty.png
an empty png of size 100x100 will be created.
