The internet is a cold dark place with only terrible secret santa generators.
This is a standalone python script that takes a file or reads from standard input a list of names and prints to standard output same names in the same order but as santa assignments:
Pipe into standard input:
echo 'Bob\nSally\nMandip' | ./secretsanta
Sally
Mandip
Bob
Or read from a file:
echo 'Bob\nSally\nMandip' > children.txt
./secretsanta children.txt > santas.txt
With just a and b the only possible output is ba:
echo 'a\nb' | ./secretsanta
b
a
This means a (which is the first line of the input) should be assigned to b
(the first line of the output).
With just a, b and c you might get bca or cab:
echo 'a\nb\nc' | ./secretsanta
b
c
a
Or maybe...
echo 'a\nb\nc' | ./secretsanta
c
a
b