As an administrator on the Unix system, we may encounter situations where we must remove the blank lines from many files. Similar is the case comments also, we may need to remove from a lot of files. Doing this using vi or nano editor is going to be lengthy and very tedious. This is also very error-prone. We can achieve this using the sed command very easily. Let’s explore how we can do that
How to delete the blank lines using sed
We can use the below command
sed '/^$/d' < file name>
The above will not touch the file, it will provide the output with the blank lines
Example $cat test.txt aaaaa bbbb CCCCC ddddd $sed '/^$/d' test.txt aaaaa bbbb CCCCC ddddd
Now if we want to remove the blank lines from the file itself
sed -i '/^$/d' < file name>
The above command will change the file itself
Example $cat test.txt aaaaa bbbb CCCCC ddddd $sed -i '/^$/d' test.txt $cat test.txt aaaaa bbbb CCCCC ddddd
We can change multiple files also using the same command.
sed -i '/^$/d' *txt
How to backup the files before deleting the blank lines
This can be done using the command
sed -i.bak '/^$/d' *txt
- This will make a backup of all the files with the “.bak” extension before changing it
- Remember there is no space after i
How to remove comment using sed
This can be done using the below command
sed -i '/^#//' < file name>
Example $cat test.txt #aaaaa bbbb CCCCC #ddddd $sed -i '/^#//' test.txt $cat test.txt aaaaa bbbb CCCCC ddddd
How to remove the commented lines from the file
This can be done using the below command
sed -i 's/#.*//' <file name> Example $cat test.txt #aaaaa bbbb CCCCC #ddddd $sed -i '/#.*//' test.txt $cat test.txt bbbb CCCCC $
How to delete the commented and blank lines
We can achieve this using d in sed
sed -i '/^#\|^$/d' <file name> Example $cat test.txt #aaaaa bbbb CCCCC #ddddd $sed -i '/^#\|^$/d' test.txt $cat test.txt bbbb CCCCC $
Hope you like this article
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