minix3下安装libevent-蒲公英云

libevent是一个c语言编写的事件框架，支持异步IO、定时器、信号事件。它支持跨平台，大部分都是在linux下安装并使用，今天介绍在unix系统minix3上的安装。
minix3上编译环境是clang,clang++，并不是我们常见的gcc,g++，所以在进行源码编译的时候，需要指定系统编译器。再一个就是minix3上没有/usr/local这个目录，如果直接configure安装不指定libevent安装前缀prefix，那么它就会安装到/usr/local目录下，这个目录并不是系统设定的，所以它的包含文件，库目录文件不会被系统搜索到，最后在使用libevent库的时候，需要我们手动添加include dir,lib dir，为了减少不必要的麻烦，我们指定configure时的前缀prefix为/usr，这样，libevent的头文件会安装到/usr/include下，而依赖库文件会安装到/usr/lib目录下。
编译安装过程：
1、下载libevent，这里官网是[https://libevent.org/][https_libevent.org]，下载地址是：[https://github.com/libevent/libevent/releases/download/release-2.1.10-stable/libevent-2.1.10-stable.tar.gz][https_github.com_libevent_libevent_releases_download_release-2.1.10-stable_libevent-2.1.10-stable.tar.gz]。
2、解压
3、configure、make 、 make install安装三步曲。
这里进行configure的时候，需要注意，因为minix3.3.0版本没有gcc,g++，但是有clang，我们需要指定clang为c compiler，所以在configure的时候需要指定CC=/usr/pkg/bin/clang，我的这个机器本来已经安装了openssl，但是却找不到openssl.pc文件，所以提示没有找到openssl依赖库，只好禁用openssl，使用命令--disable-openssl
./configure --prefix=/usr CC=/usr/pkg/bin/clang --disable-openssl
这一步没有报错，就可以进行下面的编译和安装了
#make
#make install
下面的打印信息是我 make install的打印信息：
# make install
make  install-am
 ./install-sh -c -d '/usr/bin'
 /usr/bin/install -c event_rpcgen.py '/usr/bin'
 ./install-sh -c -d '/usr/lib'
 /bin/sh ./libtool   --mode=install /usr/bin/install -c   libevent.la libevent_core.la libevent_extra.la libevent_pthreads.la '/usr/lib'
libtool: install: /usr/bin/install -c .libs/libevent.lai /usr/lib/libevent.la
libtool: install: /usr/bin/install -c .libs/libevent_core.lai /usr/lib/libevent_core.la
libtool: install: /usr/bin/install -c .libs/libevent_extra.lai /usr/lib/libevent_extra.la
libtool: install: /usr/bin/install -c .libs/libevent_pthreads.lai /usr/lib/libevent_pthreads.la
libtool: install: /usr/bin/install -c .libs/libevent.a /usr/lib/libevent.a
libtool: install: chmod 644 /usr/lib/libevent.a
libtool: install: ranlib /usr/lib/libevent.a
libtool: install: /usr/bin/install -c .libs/libevent_core.a /usr/lib/libevent_core.a
libtool: install: chmod 644 /usr/lib/libevent_core.a
libtool: install: ranlib /usr/lib/libevent_core.a
libtool: install: /usr/bin/install -c .libs/libevent_extra.a /usr/lib/libevent_extra.a
libtool: install: chmod 644 /usr/lib/libevent_extra.a
libtool: install: ranlib /usr/lib/libevent_extra.a
libtool: install: /usr/bin/install -c .libs/libevent_pthreads.a /usr/lib/libevent_pthreads.a
libtool: install: chmod 644 /usr/lib/libevent_pthreads.a
libtool: install: ranlib /usr/lib/libevent_pthreads.a
 ./install-sh -c -d '/usr/include'
 /usr/bin/install -c -m 644 include/evdns.h include/event.h include/evhttp.h 
include/evrpc.h include/evutil.h '/usr/include'
 ./install-sh -c -d '/usr/include/event2'
 /usr/bin/install -c -m 644 include/event2/buffer.h include/event2/buffer_compat.h 
include/event2/bufferevent.h include/event2/bufferevent_compat.h 
include/event2/bufferevent_ssl.h include/event2/bufferevent_struct.h include/event2/dns.h 
include/event2/dns_compat.h include/event2/dns_struct.h include/event2/event.h 
include/event2/event_compat.h include/event2/event_struct.h include/event2/http.h 
include/event2/http_compat.h include/event2/http_struct.h include/event2/keyvalq_struct.h 
include/event2/listener.h include/event2/rpc.h include/event2/rpc_compat.h 
include/event2/rpc_struct.h include/event2/tag.h include/event2/tag_compat.h 
include/event2/thread.h include/event2/util.h include/event2/visibility.h 
'/usr/include/event2'
 ./install-sh -c -d '/usr/include/event2'
 /usr/bin/install -c -m 644 include/event2/event-config.h '/usr/include/event2'
 ./install-sh -c -d '/usr/lib/pkgconfig'
 /usr/bin/install -c -m 644 libevent.pc libevent_core.pc libevent_extra.pc libevent_pthreads.pc '/usr/lib/pkgconfig'
从中可以看出头文件全部加入了/usr/include目录，库文件加入了/usr/lib目录，这样系统就能找到他们的位置了。
可以编写一个定时器来测试一下：

hello.c

#include <stdio.h>
#include <event.h>
#include <time.h>
struct event ev;
struct timeval tv;
void timer_cb(int fd, short event, void *arg)
{
    printf("timer_cb\n");
    event_add(&ev, &tv);
}
int main()
{
    struct event_base *base = event_init();
    tv.tv_sec = 1;
    tv.tv_usec = 0;
    event_set(&ev, -1, 0, timer_cb, NULL);
    event_base_set(base, &ev);
    event_add(&ev, &tv);
    event_base_dispatch(base);
    return 0;
}
编译：这里就需要手动设定依赖库
#clang -o hello hello.c -levent

编译运行打印信息：

# clang -o hello hello.c 
/var/tmp/hello-2fbefe.o: In function `timer_cb':
hello.c:(.text+0x43): undefined reference to `event_add'
/var/tmp/hello-2fbefe.o: In function `main':
hello.c:(.text+0x81): undefined reference to `event_init'
hello.c:(.text+0xcc): undefined reference to `event_set'
hello.c:(.text+0xe1): undefined reference to `event_base_set'
hello.c:(.text+0xfc): undefined reference to `event_add'
hello.c:(.text+0x10a): undefined reference to `event_base_dispatch'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
# clang -o hello hello.c -levent
# ./hello
timer_cb
timer_cb
timer_cb
timer_cb
^C
#
 不设定依赖库，编译报错；若编译通过直接运行，控制台会间隔1秒打印timer\_cb。