Why piping to the same file doesn't work on some platforms?

Question

In cygwin, the following code works fine

$ cat junk
bat
bat
bat

$ cat junk | sort -k1,1 |tr \'b\' \'z\' > junk

$ cat junk
zat
zat
zat

Answer 1

You want to edit that file, you can just use the editor.

ex junk << EOF
%!(sort -k1,1 |tr 'b' 'z')
x
EOF