The other day I had to prepare a very large data source before importing it into the database. So here is a nice tool to help you with this kind of task that your IDE might refuse to do for you.
The tool I want to show to you today is the command line tool
sed. In short it is a tool to search and replace with an easy syntax. Out of the box it works with input streams and files alike, what makes it easy to work with it in a chain of commands.
The data source I had to update was a list of airports from openflights.org. Unfortunately Sublime-Text refused to execute the regular expression I tried to execute on the file, so I had to find something else.
Of course the tool I used in the end was
sed. Here are some examples to show how it works.
sed 's/search/repalce/g' input.txt
This command will search for
search in the
input.txt file and replace it with
replace. Note that this will just return the output back to the standard output. Use the
-i flag to write back to the input file.
sed -i 's/search/repalce/g' input.txt
As you can see,
sed uses regular expressions to search and replace.
Here is a more useful example of
sed in action. The following command will replace all empty lines in the file input file.
sed -i '/^$/d' input.txt
What I had to do on the list of airports from openflights.org, was to remove all entries that are not located in Europe. Fortunately for me, the timezone of the airports is also available in the list of airports. So I could remove all entries that do not have the string
Europe in it. And this is how this can be done with
sed -i '/Europe/!d' input.txt
As you can see,
sed is a nice little command to add to your toolbox. Have some fun with it 😁