$ echo "Hello"| 7zr a -si hello.txt.7z
Creating archive hello.txt.7z

Compressing  [Content]

Everything is Ok

$ echo "Hello"| 7zr a -si hello.txt.7z
Updating archive hello.txt.7z

Compressing  [Content]

Everything is Ok

$ echo "Hello"| 7zr a -si hello.txt.7z

Error:
Duplicate filename:
hello.txt
hello.txt

7zr a foo.7z foo

7zr u foo.7z -up1q0r2y2 foo

<input> | 7zr a -sifoo foo.7z