Linux libcurl安装及注意事项

 一、下载

           官网下载地址 ：  https://curl.haxx.se/download.html

           选择最新的一个即可。

         

二、安装

    1、解压

         下载到的压缩包为curl-7.51.0.tar.gz，使用命令  tar -zxvf curl-7.51.0.tar.gz   解压。

     2、进入解压出的目录curl-7.51.0，执行

       （1）sudo ./configure

       （2）sudo make  

       （3）sudo make install

         安装完成，在命令行测试是否可用，直接输入curl，出现如下情况安装基本成功

         如果提示该命令不存在。则执行以下命令：

                 export PATH=$PATH:/usr/local/curl/bin

  

        检查/usr/include/里有没有crul没有的话，需要把解压出的include文件夹下的文件复制过去。

                cp -r curl-7.51.0/include/curl/ /usr/include/

         检查库和头文件

[root@localhost curl-7.51.0]# curl-config --cflags

-I/usr/local/include

 

[root@localhost curl-7.51.0]# curl-config --libs

-L/usr/local/lib -lcurl

            以后使用gcc编译使用libcurl的c代码，都需加上-lcurl。

三、编译代码

          使用libcurl官网的例子，只稍微修改。

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ | |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

#include <stdio.h>

#include <curl/curl.h>

/* <DESC>
 * Get a single file from an FTPS server.
 * </DESC>
 */

struct FtpFile {
  const char *filename;
  FILE *stream;
};

static size_t my_fwrite(void *buffer, size_t size, size_t nmemb,
                        void *stream)
{
  struct FtpFile *out=(struct FtpFile *)stream;
  if(out && !out->stream) {
    /* open file for writing */
    out->stream=fopen(out->filename, "wb");
    if(!out->stream)
      return -1; /* failure, can't open file to write */
  }
  return fwrite(buffer, size, nmemb, out->stream);
}


int main(void)
{
  CURL *curl;
  CURLcode res;
  struct FtpFile ftpfile={
    "yourfile.bin", /* name to store the file as if successful */
    NULL
  };

  printf("come in");
  return 0;

  curl_global_init(CURL_GLOBAL_DEFAULT);

  curl = curl_easy_init();
  if(curl) {
    /*
     * You better replace the URL with one that works! Note that we use an
     * FTP:// URL with standard explicit FTPS. You can also do FTPS:// URLs if
     * you want to do the rarer kind of transfers: implicit.
     */
    curl_easy_setopt(curl, CURLOPT_URL,
                     "ftp://user@server/home/user/file.txt");
    /* Define our callback to get called when there's data to be written */
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, my_fwrite);
    /* Set a pointer to our struct to pass to the callback */
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &ftpfile);

    /* We activate SSL and we require it for both control and data */
    curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_ALL);

    /* Switch on full protocol/debug output */
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

    res = curl_easy_perform(curl);

    /* always cleanup */
    curl_easy_cleanup(curl);

    if(CURLE_OK != res) {
      /* we failed */
      fprintf(stderr, "curl told us %d
", res);
    }
  }

  if(ftpfile.stream)
    fclose(ftpfile.stream); /* close the local file */

  curl_global_cleanup();

  return 0;
}

编译：gcc ftpsget.c -o ddd.out -lcurl

执行：

可能会出现的问题：error while loading shared libraries: libcurl.so.4: cannot open shared object file: No such file or directory

解决方法：

查找 libcurl所有相关的so库所在位置，在/etc/ld.so.conf中加入libcurl有关so库所在目录。

进入根目录/，执行find -name *libcurl.so*，就会发现所在目录。

 

在/etc/ld.so.conf中加入   /usr/local/lib    这一行，

保存/etc/ld.so.conf

 

执行命令  /sbin/ldconfig -v  生效。