Bash #!/bin/bash # Fibonacci numbers # Writes an infinite series to stdout, one entry per line function fib() { local a=1 local b=1 while true ; do echo $a local tmp=$a a=$(( $a + $b )) b=$tmp done } # output the 10th element of the series and halt fib | head -10 | tail -1 Bash w/ language specified #!/bin/bash # Fibonacci numbers # Writes an infinite series to stdout, one entry per line function