37 articles

Linux: display images type and size in command line

Front-end developers probably often need to verify the properties of some images like their type or their dimensions. To avoid firing Gimp or similar software just for a quick look, GNU/Linux distributions1 offer as usual handy tools like identify, coming from the ImageMagick suite.

$ identify /home/didier/images/myimage.jpg

[...] Display full article

Apache: enable HTTPS

To enable HTTP Secure (HTTPS) on Apache, we first enable the modules called mod_ssl and mod_socache_shmcb in the main Apache configuration file, located at /etc/httpd/conf/httpd.conf:

LoadModule socache_shmcb_module modules/mod_socache_shmcb.so
LoadModule ssl_module modules/mod_ssl.so

We include SSL own configuration file:

# Secure (SSL/TLS

[...] Display full article

MariaDB / MySQL: generate a row number

There is currently no built-in method to return row numbers. The solution is to use a variable which is incremented in each row, like this:

@currentRow := @currentRow + 1 AS rowNumber

We can use a JOIN statement to initialise the variable without SET:

JOIN (SELECT @currentRow := 0) row

Another notation, replacing JOIN with a comma: [...] Display full article

Delete lines containing a specific string with sed

The following command makes sed delete every lines containing the matching pattern from the file named foo. If this file is important, we make sure to back it up first!

$ sed -i '/pattern/d' /path/to/foo

The -i flag (GNU version only) edit the file in-place. For non-GNU version, we can redirect the output with >.

$ sed '/pattern/d' /path/to/foo > /path/to/foo

MariaDB / MySQL: export or backup data to a CSV file

It seems there are several ways to do this. Here is one, using the mysql prompt. I used mysql root account because my usual user has not enough permissions to write files (ERROR 1045 (28000): Access denied for user 'username'@'localhost' (using password: YES)), even after a chmod 777: UPDATE: We need to grant file access to the database user:

$ mysq

[...] Display full article

MariaDB / MySQL: backup and restore a specific table

We just have to specify the name of the table we want to backup in the usual mysqldump command:

$ mysqldump -h hostname -u username -p database_name table_name > backup_table_name.sql

Then, to restore it:

mysql -u username -p database_name < /path/to/backup_table_name.sql


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