ptee is a Unix shell tool similar to tee, but it allows you to invoke multiple sub-shells in parallel. Standard input to ptee is copied to both normal standard output and to each sub-shell running under ptee. Each sub-command is run concurrently and fed the same input. The output of each sub-command is thrown away, but any shell expression can be used, such as redirecting to a file. Note that there are some limits on ptee. The shell pipeline will only execute at the pace of the slowest sub-command; otherwise large amounts of data would have to be buffered. Also, the shell that ptee invokes requires 'sh'-like semantics, such as supporting the -c option.