/usr/share/zsh/help/let is in zsh-common 5.1.1-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | let arg ...
Evaluate each arg as an arithmetic expression. See the section
`Arithmetic Evaluation' in zshmisc(1) for a description of
arithmetic expressions. The exit status is 0 if the value of
the last expression is nonzero, 1 if it is zero, and 2 if an
error occurred.
|