/usr/share/aclocal/zshoot.m4 is in zsh-dev 5.1.1-1ubuntu2.3.
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 7 8 | AC_DEFUN([zsh_OOT],
[
AC_CHECK_HEADERS(stdarg.h varargs.h termios.h termio.h)
AC_TYPE_SIGNAL
AC_DEFINE([ZSH_OOT_MODULE], [], [Out-of-tree module])
])
|