make: flex: 命令未找到

Question

我对 Linux 很陌生。我在 vmware 上使用 Xubuntu 14.10，我正在尝试制作一个可执行文件。我make在终端中输入，但该过程因错误而停止：

flex -Pfct_pddl lex-fct_pddl.l
make: flex: Command not found
makefile:66: recipe for target 'lex.fct_pddl.c' failed
make: *** [lex.fct_pddl.c] Error 127

据我了解，我需要安装 flex。我试着这样做：

sudo apt-get install flex

但我得到了这个：

Package flex is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'flex' has no installation candidate

知道我应该做什么吗？谢谢。

Answer 1

尝试这个：

打开终端，

按Ctrl+ Alt+T

运行：

sudo -i
nano /etc/apt/sources.list

在打开的文件中，删除其内容并放置：

deb http://old-releases.ubuntu.com/ubuntu/ utopic main restricted
deb-src http://old-releases.ubuntu.com/ubuntu/ utopic main restricted
deb http://old-releases.ubuntu.com/ubuntu/ utopic-updates main restricted
deb-src http://old-releases.ubuntu.com/ubuntu/ utopic-updates main restricted
deb http://old-releases.ubuntu.com/ubuntu/ utopic universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ utopic universe multiverse
deb http://old-releases.ubuntu.com/ubuntu utopic-security main restricted
deb-src http://old-releases.ubuntu.com/ubuntu utopic-security main restricted
deb http://old-releases.ubuntu.com/ubuntu/ utopic-backports main restricted universe multiverse

Ctrl+O 保存文件

Ctrl+X 关闭纳米

继续运行：

apt-get update
apt-get dist-upgrade
apt-get install flex