libuv的学习与链接库问题：error while loading shared libraries: libuv.so.1

最近学习了一下另一个网络库：libuv，一个文档少，开始令人一头雾水，然后还是很好用的一个库。当然学习该库最重要的原则就是------去看“uv.h”头文件，里面有你想知道的一切。

1. 改了uv_book中的一个例子代码如下：

a.下面的是client

#include 
#include 
#include 
#include 
#include 
#include 

uv_loop_t *loop;
uv_tcp_t *client;

void alloc_buffer(uv_handle_t* handle, size_t suggested_size, uv_buf_t* buf);

void do_read();

void do_write();

void echo_write(uv_write_t *req, int status);

void echo_read(uv_stream_t *client_, ssize_t nread, const uv_buf_t* buf) ;

void on_connection(uv_connect_t* req, int status);

void alloc_buffer(uv_handle_t* handle, size_t suggested_size, uv_buf_t* buf) {
    *buf = uv_buf_init((char*) malloc(suggested_size), suggested_size);
}

void do_read()
{
    int r = uv_read_start((uv_stream_t*) client, alloc_buffer, echo_read);  
    if(r<0)
    {
        fprintf(stderr, "Read error %s\n", uv_err_name(r));
        uv_close((uv_handle_t*)client, NULL);
    }
}

void do_write()
{
    uv_write_t *req_write = (uv_write_t *) malloc(sizeof(uv_write_t));  

    char *line = (char*)malloc(1024*sizeof(char));
    memset(line, 0, 1024);
    int len = 0;
    while (gets(line))
    {
      for(; len<1024; len++)
      {
          if(line[len] == 0)
              break;
      }
      break;
    }

    uv_buf_t *buf = (uv_buf_t*)malloc(sizeof(uv_buf_t));
    uv_buf_init(line, len+1);
    buf->base = line;
    buf->len = len+1;
    req_write->data = (void*) buf->base;
    int r = uv_write(req_write, (uv_stream_t*)client, buf, 1, echo_write);
    if(r<0)
    {
        fprintf(stderr, "write error %s\n", uv_err_name(r));
        uv_close((uv_handle_t*)client, NULL);
    }
}

void echo_write(uv_write_t *req, int status)
{
    if (status < 0) {
        fprintf(stderr, "Write error %s\n", uv_err_name(status));
    }
    char *base = (char*) req->data;
    free(base);
    free(req);

    do_write();
}

void echo_read(uv_stream_t *client_, ssize_t nread, const uv_buf_t* buf)
{
    if (nread < 0) {
        if (nread == UV_EOF){
            fprintf(stderr, "UV_EOF....\n");
        }else{
            fprintf(stderr, "Read error %s : %s\n", uv_err_name(nread), uv_strerror(nread));
        }
        uv_close((uv_handle_t*) client_, NULL);
        return;
    }else{
        printf("%s\n", buf->base);
    }

    do_read();
}

void on_connection(uv_connect_t* req, int status) {
    if (status < 0) {
        // error!
        fprintf(stderr, "connect error %s : %s\n", uv_err_name(status), uv_strerror(status));
        return;
    }

    free(req);

    do_read();
    do_write();

}

int main() {
    loop = uv_default_loop();

    client = (uv_tcp_t *)malloc(sizeof(uv_tcp_t));
    uv_tcp_init(loop, client);

    struct sockaddr_in bind_addr;
    uv_ip4_addr("127.0.0.1", 7000, &bind_addr);

    uv_connect_t *req = (uv_connect_t *)malloc(sizeof(uv_connect_t));
    int r = uv_tcp_connect(req, client, (const sockaddr*)&bind_addr, on_connection);
    if (r) {
        fprintf(stderr, "connect error %s\n", uv_err_name(r));
        return 1;
    }
    return uv_run(loop, UV_RUN_DEFAULT);
}

b.下面的是server

#include 
#include 
#include 
#include 

uv_loop_t *loop;

void alloc_buffer(uv_handle_t* handle, size_t suggested_size, uv_buf_t* buf) {
    *buf = uv_buf_init((char*) malloc(suggested_size), suggested_size);
}

void echo_write(uv_write_t *req, int status) {
    if (status < 0) {
        fprintf(stderr, "Write error %s\n", uv_err_name(status));
    }
    char *base = (char*) req->data;
    free(base);
    free(req);
}

void echo_read(uv_stream_t *client, ssize_t nread, const uv_buf_t* buf) {
    if (nread < 0) {
        if (nread == UV_EOF){
            fprintf(stderr, "UV_EOF....\n");
        }else{
            fprintf(stderr, "Read error %s : %s\n", uv_err_name(nread), uv_strerror(nread));
        }
        uv_close((uv_handle_t*) client, NULL);
        return;
    }

    printf("%s\n", buf->base);

    uv_write_t *req = (uv_write_t *) malloc(sizeof(uv_write_t));    //alloc write watcher
    req->data = (void*) buf->base;
    uv_write(req, client, buf, 1, echo_write);
}

void on_new_connection(uv_stream_t *server, int status) {

    printf("enter on_new_connection...\n");

    if (status == -1) {
        // error!
        return;
    }

    uv_tcp_t *client = (uv_tcp_t*) malloc(sizeof(uv_tcp_t));
    uv_tcp_init(loop, client);
    if (uv_accept(server, (uv_stream_t*) client) == 0) {
        int r = uv_read_start((uv_stream_t*) client, alloc_buffer, echo_read);  
        if(r<0)
        {
            fprintf(stderr, "Read error %s\n", uv_err_name(r));
            uv_close((uv_handle_t*)client, NULL);
        }
    }
    else {
        uv_close((uv_handle_t*) client, NULL);
    }
}

int main() {
    loop = uv_default_loop();

    uv_tcp_t server;
    uv_tcp_init(loop, &server);

    struct sockaddr_in bind_addr;
    uv_ip4_addr("0.0.0.0", 7000, &bind_addr);
    uv_tcp_bind(&server, (const sockaddr*)&bind_addr, 0);    //0--ipv4; 1--ipv6
    int r = uv_listen((uv_stream_t*) &server, 128, on_new_connection);
    if (r) {
        fprintf(stderr, "Listen error %s\n", uv_err_name(r));
        return 1;
    }
    return uv_run(loop, UV_RUN_DEFAULT);
}

注：所有回调函数的格式在“uv.h”中都能找到。先执行server，再执行client。

2. 用的libuv的版本是libuv-v1.9.1，编译程序完毕后，执行的时候出现如下错误：

------------error while loading shared libraries: libuv.so.1: cannot open shared object file : No such file---------------

用 “ldd” 查看需要的库时，的确 “libuv.so.1” 说未被发现，可是查看 “/usr/local/bin” 明明是存在该库的。

------------------------------------------------------------------解决办法----------------------------------------------------------------

3. <方法1> 执行 “ldconfig” 命令，该命令可让动态链接库为系统所共享。发生错误的原因就是安装libuv库后，没有更新系统链接库名字列表，导致系统找不到该库。

    <方法2> 编译的时候指定动态链接库链接路径， 用gcc编译时，添加 “-Wl,-rpath=动态库路径”即可。