I am trying to use Curl in C.

我正在尝试使用C++中的Curl。

I visited Curl official page, and copied sample source code.

我访问了Curl官方页面，并复制了样例源代码。

below is the link:
http://curl.haxx.se/libcurl/c/sepheaders.html

以下是链接：http://curl.haxx.se/libcurl/c/sepheaders.html

when I run this code with command "gcc test.c",

当我使用“GCC测试.c”命令运行这段代码时，

the console shows message like below.

控制台显示如下消息。

/tmp/cc1vsivQ.o: In function `main':
test.c:(.text+0xe1): undefined reference to `curl_global_init'
test.c:(.text+0xe6): undefined reference to `curl_easy_init'
test.c:(.text+0x10c): undefined reference to `curl_easy_setopt'
test.c:(.text+0x12e): undefined reference to `curl_easy_setopt'
test.c:(.text+0x150): undefined reference to `curl_easy_setopt'
test.c:(.text+0x17e): undefined reference to `curl_easy_cleanup'
test.c:(.text+0x1b3): undefined reference to `curl_easy_cleanup'
test.c:(.text+0x1db): undefined reference to `curl_easy_setopt'
test.c:(.text+0x1e7): undefined reference to `curl_easy_perform'
test.c:(.text+0x1ff): undefined reference to `curl_easy_cleanup'

I do not know how to solve this.

我不知道怎么解决这个问题。

You don't link with the library.

你没有链接到图书馆。

When using an external library you must link with it:

使用外部库时，必须与其链接：

$ gcc test.c -lcurl

The last option tells GCC to link (-l) with the library curl.

最后一个选项告诉GCC将(-L)与库卷曲链接。

In addition to Joachim Pileborg's answer, it is useful to remember that gcc/g++ linking is sensitive to order and that your linked libraries must follow the things that depend upon them.

除了Joachim Pileborg的回答之外，记住GCC/g++链接对顺序是敏感的，并且您的链接库必须遵循依赖于它们的东西，这一点很有用。

$ gcc -lcurl test.c

$GCC-lcurl测试.c

will fail, missing the same symbols as before. I mention this because I came to this page for forgetting this fact.

将失败，缺少与以前相同的符号。我提到这一点是因为我来到这个页面是为了忘记这个事实。

I have the same problem, but i use g++ with a make file.
This is a linker issue.
You need to add option -lcurl on the compiler and on the linker.
In my case on the make file:

我也有同样的问题，但我使用了带有make文件的g++。这是一个链接器问题。您需要在编译器和链接器上添加选项-lcurl。在我的Make文件中：

CC ?= gcc
CXX ?= g++
CXXFLAGS += -I ../src/ -I ./ -DLINUX -lcurl  <- compile option
LDFLAGS += -lrt -lpthread -lcurl      <- linker option

Gerard

杰拉德

Depending how bad things are you might need an -L/somewhere in LDFLAGS to let the linker know where the libraries are. ldconfig is supposed to pick them up and find them on every boot but on a new machine it can take a little prodding, like adding a directory to your /etc/ld.so.conf.

根据情况的不同，您可能需要在LDFLAGS中的某个地方使用-L/来让链接器知道库在哪里。Ldconfig应该会在每次引导时获取并找到它们，但在一台新机器上可能需要一些刺激，比如将一个目录添加到您的/etc/ld.so.conf中。

I had the same problem and found another line among it : "libcurl-x86.lib : warning LNK4272: library machine type 'x64' conflicts with target machine type 'x86'" which means the lib was 64 bit, while i was compiling for 32 bit.

我也遇到了同样的问题，并在其中找到了另一行：“libcurl-x86.lib：Warning LNK4272：库机器类型‘x64’与目标机器类型‘x86’冲突”，这意味着当我编译32位时，库是64位的。