Often you may want to use sed to extract only numbers from a string.
You can use the following syntax to do so:
sed "s/[^0-9]//g" employees.txt
This particular example extracts only the numbers from each line in the file named employees.txt.
Here is what the various sed commands do:
- s: Used to “substitute” one pattern for another pattern
- [^0-9]: Matches all characters in the string that are not numbers
- //: Replaces the matched characters with nothing, which effectively removes all characters that are not numbers
- g: Specifies that this substitution should be made “globally”, i.e. for all occurrences
The following example shows how to use this syntax in practice.
Example: How to Use sed to Extract Numbers from a String
Suppose that we have the following file named employees.txt that contains ID numbers for various employees at some company:
Suppose that we would like to extract only the numbers from each employee ID.
We can use the following syntax to do so:
sed "s/[^0-9]//g" employees.txt
The following screenshot shows how to use this syntax in practice:
Notice that this returns only the numbers from each line in the file.
Note that we could also use the > command to save these results to a new file:
sed "s/[^0-9]//g" employees.txt > employees_new.txt
This particular example would extract the numbers from each line in the file named employees.txt and save the results to a new file named employees_new.txt.
Related Tutorials
The following tutorials explain how to perform other common tasks in sed:
How to Use sed to Extract All Lines Containing a Pattern
How to Use sed to Replace All Occurrences of Pattern
How to Use sed to Replace All Text After Match
