Often you may want to use sed to delete all lines from a file that start with a specific pattern.
You can use the following basic syntax to do so:
sed -i '/^##/d' cities.txt
This particular example deletes all lines that start with the pattern ## in the file named teams.txt.
Note that we use the -i flag in sed to delete the lines in-place.
If you’d like to store the results to a new file then you can use the following syntax:
sed '/^##/d' cities.txt > cities_new.txt
The following example shows how to use this syntax in practice.
Note: The ^ operator is used to find the start of a string.
Example: Use sed to Delete All Lines Starting with Specific Pattern
Suppose we have a text file named cities.txt that contains the names of various U.S. cities:
Suppose that we would like to delete all lines from the file that start with the pattern ##.
We can use the following syntax to do so:
sed -i '/^##/d' cities.txt
The following screenshot shows how to use this syntax in practice:
Notice that when we use the cat command again to view the contents of the file that all lines starting with ## have been removed from the file.
Note that we could also use the following syntax to instead remove all lines starting with ## and save the results to a new file:
sed '/^##/d' cities.txt > cities_new.txt
The following screenshot shows how to use this syntax in practice:
Notice that when we use the cat command to view the contents of the file named cities_new.txt that it contains all lines from the original file with the lines starting with ## removed.
Related Tutorials
The following tutorials explain how to perform other common tasks in sed:
How to Use sed to Replace All Occurrences of Pattern
How to Use sed to Replace All Text After Match
How to Use sed to Extract All Lines Containing a Pattern
