http client - libcurl

http client - libcurl

참고:

• libcurl - https://curl.haxx.se/libcurl/
• libcurl get - https://curl.haxx.se/libcurl/c/simple.html
• libcurl post - https://curl.haxx.se/libcurl/c/post-callback.html
• HTTP test server - https://httpbin.org/ 

Http get sample

• http get
• 응답 데이터를 .out 파일로 저장

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>


static size_t cb_write(void * contents, size_t size, size_t nmemb, void * userp)
{
    FILE * fp = (FILE*)userp;
    fwrite(contents, size, nmemb, fp);
    return size * nmemb;
}

static void dumpfile(const char * path);

int main(int argc, char *argv[])
{
    FILE * out;
    CURLcode res;
    CURL * curl;

    curl_global_init(CURL_GLOBAL_ALL);

    curl = curl_easy_init();
    if (!curl) {
        printf("curl_easy_init() failed\n");
        exit(1);
    }

    out = fopen(".out", "wb");
    if (!out) {
        printf("fopen() failed\n");
        exit(1);
    }

    curl_easy_setopt(curl, CURLOPT_URL, "http://httpbin.org/get");
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, cb_write);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)out);
    res = curl_easy_perform(curl);
    if (res != CURLE_OK) {
        fclose(out);
        printf("curl_easy_perform() failed\n");
        exit(1);
    }
    fclose(out);

    dumpfile(".out");

    curl_easy_cleanup(curl);

    curl_global_cleanup();

    return 0;
}

static void dumpfile(const char * path) {
    int len;
    char buf[1024] = {0,};
    FILE * fp = fopen(path, "rb");
    if (!fp) {
        perror("fopen() failed");
        exit(1);
    }

    while ((len = fread(buf, sizeof(char), sizeof(buf), fp)) > 0) {
        printf("%.*s", len, buf);
    }

    fclose(fp);
}
 

빌드

$ gcc -o httpget main.c `pkg-config --cflags --libs libcurl`

실행

$ ./httpget
{
  "args": {},
  "headers": {
    "Accept": "*/*",
    "Connection": "close",
    "Host": "httpbin.org"
  },
  "origin": "xx.xx.xx.xx",
  "url": "http://httpbin.org/get"
}

Http post sample

• http post
• Content-Type: text/plain

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

static size_t cb_write(void * contents, size_t size, size_t nmemb, void * userp)
{
    FILE * fp = (FILE*)userp;
    fwrite(contents, size, nmemb, fp);
    return size * nmemb;
}

static void dumpfile(const char * path);

int main(int argc, char *argv[])
{
    struct curl_slist * headers = NULL;
    static const char * msg = "hello world";
    FILE * out;
    CURLcode res;
    CURL * curl;

    curl_global_init(CURL_GLOBAL_ALL);

    curl = curl_easy_init();
    if (!curl) {
        printf("curl_easy_init() failed\n");
        exit(1);
    }

    out = fopen(".out", "wb");
    if (!out) {
        printf("fopen() failed\n");
        exit(1);
    }

    headers = curl_slist_append(headers, "Content-Type: text/plain");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

    curl_easy_setopt(curl, CURLOPT_URL, "http://httpbin.org/post");
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(curl, CURLOPT_POST, 1L);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, msg);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, strlen(msg));
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, cb_write);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)out);
    res = curl_easy_perform(curl);
    curl_slist_free_all(headers);
    if (res != CURLE_OK) {
        fclose(out);
        fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        exit(1);
    }
    fclose(out);
    dumpfile(".out");
    curl_easy_cleanup(curl);
    curl_global_cleanup();

    return 0;
}

static void dumpfile(const char * path) {
    int len;
    char buf[1024] = {0,};
    FILE * fp = fopen(path, "rb");
    if (!fp) {
        perror("fopen() failed");
        exit(1);
    }

    while ((len = fread(buf, sizeof(char), sizeof(buf), fp)) > 0) {
        printf("%.*s", len, buf);
    }

    fclose(fp);
}

빌드

$ gcc -o httppost main.c `pkg-config --cflags --libs libcurl`

실행

$ ./httppost
{
  "args": {},
  "data": "hello world",
  "files": {},
  "form": {},
  "headers": {
    "Accept": "*/*",
    "Connection": "close",
    "Content-Length": "11",
    "Content-Type": "text/plain",
    "Host": "httpbin.org"
  },
  "json": null,
  "origin": "xx.xx.xx.xx",
  "url": "http://httpbin.org/post"
}