How to select n random lines in Bash?

How to select n random lines in Bash?

In a Bash script, I want to pick out N random lines from input file and output to another file. How can this be done? Use shuf with the -n option as shown below, to get N random lines: Sort the file randomly and pick first 100 lines: Of course <$input_file can be replaced with any piped standard input.

How to randomize lines in a file in Linux?

In addition to the shuf and sort -R, we can also shuffle lines in a file by ourselves. As the title indicates, we’ll do it in three steps: Add a random number as a prefix on each line. Sort the lines by the prefix number. Remove the prefix. 5.1. Get a Random Number

How to print lines from file backwards in Bash?

As you asked to do it in bash, here is a solution that doesn’t make use of awk, sed or perl, just a bash function: As expected. But beware that lines are stored in memory, one line in each recursively called instance of the function. So careful with big files. The awk prefixes each line with the line number followed by a space.

How do I sort text file in Linux?

The sort command is used to sort the lines of a text file in Linux. You can provide several command line options for sorting data in a text file. Here is an example file: To sort the file in alphabetical order, we can use the sort command without any options: To sort in reverse, we can use the -r option: We can also sort on the column.

How to select random lines from a file stack?

Of course <$input_file can be replaced with any piped standard input. This ( sort -R and $’… …’ to get sed to match tab chars) works with GNU/Linux and BSD/macOS. Well According to a comment on the shuf answer he shuffed 78 000 000 000 lines in under a minute.

What’s the best way to find a random number?

The standard way to find a random number between 1 and N is to take the value of random number modulo N. We want a random number between 0 and the length of our array. Here’s the approach, broken into two lines for clarity’s sake:

How can I select random files from a directory in Bash?

A simple solution for selecting 5 random files while avoiding to parse ls. It also works with files containing spaces, newlines and other special characters: Replace echo with the command you want to execute for your files.

How does a random number shuffle algorithm work?

The behavior of the algorithm changes based on how many lines are shuffled at the same time. By default, it takes every single line in turn (1, 2, 3, …, n), generates a random number from 1 to n for it, which is the new position, and moves the line to this new place.

What’s the best way to generate random numbers?

Randomly rearrange the letters in a string, sentence, or text. Randomly shuffle the order of all words in the input data. Randomly shuffle text lines and rearrange their order. Randomly shuffle paragraphs and change their order. Randomly pick an item from many items. Quickly generate random passwords. Quickly generate random numbers.

How to randomly sample a subset of a file?

My sample tool will only use 8 bytes per line, which means that very large files can be sampled from with much less memory. In contrast, the shuf and other tools mentioned above can read the entire file into system memory, which can often lead to out-of-memory errors.