Often you may want to use Bash to select N random lines from a file.
The easiest way to do so is by using the shuf command to “shuffle” the lines in the file and then by using the -n command to specify how many lines to select from the file.
You can use the following syntax to do so:
shuf -n 5 teams.txt
This particular example selects 5 random lines from the file named teams.txt.
You can also use the > command to save these random lines to a new file:
shuf -n 5 teams.txt > teams_new.txt
This particular example selects 5 random lines from the file named teams.txt and saves the lines to a new file name teams_new.txt.
The following example shows how to use this syntax in practice.
Example: How to Select Random Lines from File Using Bash
Suppose that we have a file named teams.txt in our current directory that contains the names of various basketball teams.
We can use the cat command to first view the contents of this file:
Suppose that we would like to randomly select five lines from this file.
We can use the following syntax to do so:
shuf -n 5 teams.txt
The following screenshot shows how to use this syntax in practice:
Notice that this returns five random lines from the file.
Note that we could also use the following syntax to select five random lines and then save the lines to a new file named teams_new.txt:
shuf -n 5 teams.txt > teams_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 teams_new.txt file we can see that it contains the names of five randomly selected basketball team names.
Note: Feel free to change the number provided after the -n operator to instead randomly select a different number of rows from the file.
Related Tutorials
The following tutorials explain how to perform other common tasks in Bash:
Bash: How to Generate Random Number in Range
Bash: How to Check if String Starts with Specific Value
Bash: How to Count Number of Words in String
Bash: How to Count Number of Characters in String
