我已执行以下命令，其输出如下。
CMD: sudo dpkg -i flex_2.6.1_ubuntu_16.04.deb
output:
(Reading database ... 259032 files and directories currently installed.)
Preparing to unpack flex_2.6.1_ubuntu_16.04.deb ...
Unpacking flex (2.6.1-1) over (2.6.1-1) ...
Setting up flex (2.6.1-1) ...
CMD: sudo apt-get install -f
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
libfl-dev snapd-login-service
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 17 not upgraded.
CMD: flex --version
The program 'flex' can be found in the following packages:
* flex
* flex-old
Try: sudo apt install <selected package>
CMD: dpkg -L flex | grep bin
output:
/usr/bin
/usr/bin/bin
/usr/bin/bin/flex
/usr/bin/include
/usr/bin/include/FlexLexer.h
/usr/bin/lib
/usr/bin/lib/libfl.a
/usr/bin/lib/libfl.la
/usr/bin/lib/libfl.so.2.0.0
/usr/bin/lib/libfl_pic.a
/usr/bin/lib/libfl_pic.la
/usr/bin/lib/libfl_pic.so.2.0.0
/usr/bin/share
/usr/bin/share/doc
/usr/bin/share/doc/flex
/usr/bin/share/doc/flex/AUTHORS
/usr/bin/share/doc/flex/COPYING
/usr/bin/share/doc/flex/NEWS
/usr/bin/share/doc/flex/ONEWS
/usr/bin/share/doc/flex/README
/usr/bin/share/info
/usr/bin/share/info/dir
/usr/bin/share/info/flex.info
/usr/bin/share/info/flex.info-1
/usr/bin/share/info/flex.info-2
/usr/bin/share/locale
/usr/bin/share/locale/ca
/usr/bin/share/locale/ca/LC_MESSAGES
/usr/bin/share/locale/ca/LC_MESSAGES/flex.mo
/usr/bin/share/locale/da
/usr/bin/share/locale/da/LC_MESSAGES
/usr/bin/share/locale/da/LC_MESSAGES/flex.mo
/usr/bin/share/locale/de
/usr/bin/share/locale/de/LC_MESSAGES
/usr/bin/share/locale/de/LC_MESSAGES/flex.mo
/usr/bin/share/locale/en@boldquot
/usr/bin/share/locale/en@boldquot/LC_MESSAGES
/usr/bin/share/locale/en@boldquot/LC_MESSAGES/flex.mo
/usr/bin/share/locale/en@quot
/usr/bin/share/locale/en@quot/LC_MESSAGES
/usr/bin/share/locale/en@quot/LC_MESSAGES/flex.mo
/usr/bin/share/locale/eo
/usr/bin/share/locale/eo/LC_MESSAGES
/usr/bin/share/locale/eo/LC_MESSAGES/flex.mo
/usr/bin/share/locale/es
/usr/bin/share/locale/es/LC_MESSAGES
/usr/bin/share/locale/es/LC_MESSAGES/flex.mo
/usr/bin/share/locale/fi
/usr/bin/share/locale/fi/LC_MESSAGES
/usr/bin/share/locale/fi/LC_MESSAGES/flex.mo
/usr/bin/share/locale/fr
/usr/bin/share/locale/fr/LC_MESSAGES
/usr/bin/share/locale/fr/LC_MESSAGES/flex.mo
/usr/bin/share/locale/ga
/usr/bin/share/locale/ga/LC_MESSAGES
/usr/bin/share/locale/ga/LC_MESSAGES/flex.mo
/usr/bin/share/locale/hr
/usr/bin/share/locale/hr/LC_MESSAGES
/usr/bin/share/locale/hr/LC_MESSAGES/flex.mo
/usr/bin/share/locale/ko
/usr/bin/share/locale/ko/LC_MESSAGES
/usr/bin/share/locale/ko/LC_MESSAGES/flex.mo
/usr/bin/share/locale/nl
/usr/bin/share/locale/nl/LC_MESSAGES
/usr/bin/share/locale/nl/LC_MESSAGES/flex.mo
/usr/bin/share/locale/pl
/usr/bin/share/locale/pl/LC_MESSAGES
/usr/bin/share/locale/pl/LC_MESSAGES/flex.mo
/usr/bin/share/locale/pt_BR
/usr/bin/share/locale/pt_BR/LC_MESSAGES
/usr/bin/share/locale/pt_BR/LC_MESSAGES/flex.mo
/usr/bin/share/locale/ro
/usr/bin/share/locale/ro/LC_MESSAGES
/usr/bin/share/locale/ro/LC_MESSAGES/flex.mo
/usr/bin/share/locale/ru
/usr/bin/share/locale/ru/LC_MESSAGES
/usr/bin/share/locale/ru/LC_MESSAGES/flex.mo
/usr/bin/share/locale/sr
/usr/bin/share/locale/sr/LC_MESSAGES
/usr/bin/share/locale/sr/LC_MESSAGES/flex.mo
/usr/bin/share/locale/sv
/usr/bin/share/locale/sv/LC_MESSAGES
/usr/bin/share/locale/sv/LC_MESSAGES/flex.mo
/usr/bin/share/locale/tr
/usr/bin/share/locale/tr/LC_MESSAGES
/usr/bin/share/locale/tr/LC_MESSAGES/flex.mo
/usr/bin/share/locale/vi
/usr/bin/share/locale/vi/LC_MESSAGES
/usr/bin/share/locale/vi/LC_MESSAGES/flex.mo
/usr/bin/share/locale/zh_CN
/usr/bin/share/locale/zh_CN/LC_MESSAGES
/usr/bin/share/locale/zh_CN/LC_MESSAGES/flex.mo
/usr/bin/share/locale/zh_TW
/usr/bin/share/locale/zh_TW/LC_MESSAGES
/usr/bin/share/locale/zh_TW/LC_MESSAGES/flex.mo
/usr/bin/share/man
/usr/bin/share/man/man1
/usr/bin/share/man/man1/flex.1
/usr/bin/bin/flex++
/usr/bin/lib/libfl.so
/usr/bin/lib/libfl.so.2
/usr/bin/lib/libfl_pic.so
/usr/bin/lib/libfl_pic.so.2
不确定这里出了什么问题，提前谢谢。