/usr/bin/what-source is in what-utils 1.0-0ubuntu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | #!/bin/sh
#
# what-source - what source package provides some binary/source package
#
# Copyright (C) 2011 Dustin Kirkland <kirkland@ubuntu.com>
#
# Authors:
# Dustin Kirkland <kirkland@ubuntu.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
apt-cache show "$1" | grep "^Filename:" | sed -e "s:\(.*\)/\(.*\)/\(.*\)/\(.*\)/.*:\4:"
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