cat file | … vs … <file

Question

Is there a case of ... or context where cat file | ... behaves differently than ... ?

Answer 1

When reading from a regular file, cat is in charge of reading the data, performs it as it pleases, and might constrain it in the way it writes it to the pipeline. Obviously, the contents themselves are preserved, but anything else could be tainted. For example: block size and data arrival timing. Additionally, the pipe in itself isn't always neutral: it serves as an additional buffer between the input and ....

Quick and easy way to make the block size issue apparent:

$ cat large-file | pv >/dev/null
5,44GB 0:00:14 [ 393MB/s] [              <=>                                  ]
$ pv /dev/null
5,44GB 0:00:03 [1,72GB/s] [=================================>] 100%