I have the following curl code, which make a request to website and retrieve data from it, it works well, but I want to store my data in a string and not in the output window. Any idea?
#include <stdio.h>
#include <curl/curl.h>
int main(void)
{
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://api.hostip.info/get_html.php?ip=xxx.xxx.xx.xxx");
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
res = curl_easy_perform(curl);
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
curl_easy_cleanup(curl);
}
return 0;
}
int http_get_response(void *buffer, size_t size, size_t rxed, char **msg_in)
{
char *c;
if (asprintf(&c, "%s%.*s", *msg_in, size * rxed, buffer) == -1) {
free(*msg_in);
msg_in = NULL;
return -1;
}
free(*msg_in);
*msg_in = c;
return size * rxed;
}
and add the following curl option in your main
char *msg_in = calloc(1,sizeof(char));
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, http_get_response);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &msg_in);
Then you will get the message in the msg_in
EDIT
do not forget to free msg_in when it become uselless in your program
free(msg_in); msg_in = NULL;
A a general (non-curl specific) method, change your standard output (path 1) (or standard error: path 2) path(s) prior to calling curl. Read the man page on dup2 to see how to duplicate a path to a specific descriptor, and the fdopen function to get a FILE * out of it.
The idea is you first dup path 1 for stdout, and/or 2 for stderr, to save copies of them somewhere. You then close the original paths. You create a pipe (man pipe) and then dup2 the second channel of the pipe to path 1 (or 2). You can now read() from the first channel of the pipe to get the output that was placed there.
Try this:
curl_easy_setopt(curl, CURLOPT_RETURNTRANSFER, true);
Related
I am trying to test libcurl for my project, but when I want to download a test file I get error:
ERROR : Unknown error
but no reason why it happens,
my code:
#include <stdio.h>
#include <curl/curl.h>
int main(int argc, char **argv) {
CURL *curl;
FILE *fp;
char name[30] = {"Test"};
char link[100] = {"ipv4.download.thinkbroadband.com/5MB.zip"};
CURLcode error;
int result;
fp = fopen(name,"Wb");
curl = curl_easy_init();
curl_easy_setopt;(curl, CURLOPT_URL, argv[1] );
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1L);
curl_easy_perform(curl);
result = curl_easy_perform(curl);
if (result = CURLE_OK)
printf("Sucessful download !");
else
printf("Could not download, ERROR : %s \n",curl_easy_strerror(error));
printf("%s",error);
fclose(fp);
curl_easy_cleanup(curl);
}
There's a bunch of errors in the code.
The argument to fopen should be a lower case "w".
You declare both error and result but should use only one.
There's a stray semicolon in the middle of this line: curl_easy_setopt;(curl, CURLOPT_URL, argv[1] );
Combined with what's already mentioned, this should work:
#include <stdio.h>
#include <curl/curl.h>
int main(int argc, char **argv) {
if(argc < 2) {
puts("URL not given");
return 1;
}
CURL *curl;
FILE *fp;
char name[30] = {"Test"};
char link[100] = {"ipv4.download.thinkbroadband.com/5MB.zip"};
CURLcode result;
fp = fopen(name,"w");
curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, argv[1] );
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1L);
result = curl_easy_perform(curl);
if (result == CURLE_OK)
printf("Sucessful download !");
else
printf("Could not download, ERROR : %s \n",curl_easy_strerror(result));
fclose(fp);
curl_easy_cleanup(curl);
return 0;
}
Don't forget to pass the URL as an argument, since you're not actually using link and don't check argc. And I advise you to learn how to use a debugger.
Complete guess - but could it have something to do with your code calling curl_easy_perform(curl); two times instead of once?
This looks suspicious:
curl_easy_perform(curl);
result = curl_easy_perform(curl);
Shouldn't it just be:
result = curl_easy_perform(curl);
Also, shouldn't link have the http prefix on it?
char link[100] = {"http://ipv4.download.thinkbroadband.com/5MB.zip"};
Regarding to your code indentation there are braces missing at least in your else path. That means that the last printf is being executed regardless of the result value...
Does it work as expected if you add the braces like this? Of course together with the other suggestions as stated by selbie and Emanuel P...
if (result == CURLE_OK) {
printf("Sucessful download !");
} else {
printf("Could not download, ERROR : %s \n",curl_easy_strerror(error));
printf("%s",error);
}
I am downloading file quite commonly with curl. However, the server does a tricky thing: it return non-200 code and still sends some data. The problem is that I have the HTTP code after the data are written, but I do not want to write anything if it is non-200. Does anyone know a way to do that without storing data on disk or memory?
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curlWriteHandler);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, ptr);
res = curl_easy_perform(curl);
if (res == CURLE_OK) {
return 0;
}
long response_code;
curl_easy_getinfo(curl_.get(), CURLINFO_RESPONSE_CODE, &response_code);
if (response_code != 200) {
return 0;
}
size_t curlWriteHandler(char* chars, size_t size, size_t nmemb, void* userp) {
// write to file
return size * nmemb;
}
Setting CURLOPT_FAILONERROR should do it for 4xx and 5xx errors.
When this option is used and an error is detected, it will cause the connection to get closed and CURLE_HTTP_RETURNED_ERROR is returned.
curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1L);
Closing connection is not good for me, it is important to reuse one. Can you think about anything else?
Unfortunately I can't find a way to make CURLOPT_FAILONERROR not close the connection.
The other option is to make the write function aware of the response. Unfortunately the curl handle is not passed into the callback.
We could make the curl variable global. Or we can take advantage of the void *userdata option to the write callback and pass in a struct containing both the curl handle and the buffer.
Here's a rough sketch demonstrating how the write callback can get access to the response code and also save the response body.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <curl/curl.h>
typedef struct {
CURL *curl;
char *buf;
} curl_write_data;
size_t curlWriteHandler(char* chars, size_t size, size_t nmemb, void* userp) {
curl_write_data *curl_data = (curl_write_data*)userp;
long response_code;
curl_easy_getinfo(curl_data->curl, CURLINFO_RESPONSE_CODE, &response_code);
printf("Response: %ld\n", response_code);
// Now we can save if we like.
if( response_code < 300 ) {
curl_data->buf = malloc(size*(nmemb+1));
strcpy(curl_data->buf, chars);
strcat(curl_data->buf, "\0");
return size * nmemb;
}
else {
return 0;
}
}
int main() {
CURL *curl = curl_easy_init();
if(!curl) {
perror("Cant' init curl");
}
curl_write_data curl_data = { .curl = curl, .buf = NULL };
curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/alsdfjalj");
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curlWriteHandler);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &curl_data);
curl_easy_perform(curl);
if( curl_data.buf ) {
puts(curl_data.buf);
}
}
I'm not sure if this is the best idea, its what I came up with.
I am trying to write curl c code to using the http webdav put method to upload a file.
Using wireshark I have tried to capture the packets, there is 301 response from the server.
When I try to put the file from the PC to webserver it works fine
Below is the code:
static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *stream)
{
size_t retcode;
curl_off_t nread;
/* in real-world cases, this would probably get this data differently
as this fread() stuff is exactly what the library already would do
by default internally */
retcode = fread(ptr, size, nmemb, stream);
nread = (curl_off_t)retcode;
fprintf(stderr, "*** We read %" CURL_FORMAT_CURL_OFF_T
" bytes from file\n", nread);
return retcode;
}
int curlApache ()
{
CURL *curl;
CURLcode res;
FILE * hd_src;
struct stat file_info;
char *file;
char *url;
char error;
file = "/bd0/filecreate.txt";
url = "http://10.1.21.14/webdav/test.txt";
curl_slist *slist = NULL;
slist = curl_slist_append(slist, "Accept: text/xml");
slist = curl_slist_append(slist, "Depth: infinity");
slist = curl_slist_append(slist, "Connection: Keep-Alive");
slist = curl_slist_append(slist, "Content-Type: text/xml");
slist = curl_slist_append(slist, "Expect:");
/* get the file size of the local file */
stat(file, &file_info);
hd_src = fopen(file, "a+");
if (hd_src == NULL)
printf("Disc full or no permission\n");
const char *str = "This is the file content";
const char read[24];
if (hd_src != NULL)
if (fputs (str, hd_src) != EOF);
if( fgets (read, 24, hd_src)!=NULL )
{
/* writing content to stdout */
puts(read);
}
/* In windows, this will init the winsock stuff */
curl_global_init(CURL_GLOBAL_ALL);
/* get a curl handle */
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_VERBOSE, 3L);
/* we want to use our own read function */
curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback);
/* enable uploading */
curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
/* HTTP PUT please */
curl_easy_setopt(curl, CURLOPT_PUT, 1L);
/* tell libcurl we can use "any" auth, which lets the lib pick one, but it also costs one extra round-trip and possibly sending of all the PUT data twice!!! */
curl_easy_setopt(curl, CURLOPT_HTTPAUTH, (long)CURLAUTH_DIGEST);
curl_easy_setopt(curl, CURLOPT_USERPWD, "admin:nimo0630");
fseek(hd_src, 0L, SEEK_END);
int file_size;
file_size = ftell(hd_src);
Curl_setopt(curl, CURLOPT_INFILE, hd_src);
Curl_setopt(curl, CURLOPT_INFILESIZE, file_size);
/* specify target URL, and note that this URL should include a file
name, not only a directory */
curl_easy_setopt(curl, CURLOPT_URL, url);
/* now specify which file to upload */
curl_easy_setopt(curl, CURLOPT_READDATA, hd_src);
/* provide the size of the upload, we specicially typecast the value
to curl_off_t since we must be sure to use the correct data size */
curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, curl_off_t)file_info.st_size);
/* Now run off and do what you've been told! */
res = curl_easy_perform(curl);
/* Check for errors */
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
if(!res) {
/* extract the available authentication types */
long auth;
res = curl_easy_getinfo(curl, CURLINFO_HTTPAUTH_AVAIL, &auth);
if(!res)
{
if(!auth)
printf("No auth available, perhaps no 401?\n");
else
{
printf("%s%s%s%s\n", \
auth & CURLAUTH_BASIC ? "Basic ":"", \
auth & CURLAUTH_DIGEST ? "Digest ":"", \
auth & CURLAUTH_NEGOTIATE ? "Negotiate ":"", \
auth % CURLAUTH_NTLM ? "NTLM ":"");
}
}
}
/* always cleanup */
curl_easy_cleanup(curl);
}
fclose(hd_src); /* close the local file */
curl_global_cleanup();
return 0;
}
There is status code 301 returned from the server
I believe you want to understand how to debug this issue. If you paste your code, a more specific answer can be provided.
First check if you are able to upload file using command line curl. This will tell you if server is working fine
Check if the options you use are provided in C API
Check the API's are not returning any error
You could use tcpdump / wireshark to capture packets on the client or server to see if packets went out and what was the http content. You may not see any packet if API failed
I'm using Curl library to create a simple C code with MSVC to download a file from a URL.
The problem is if the connection breaks in the middle of download my code will freeze and the unfinished file hasn't removed from the directory.
What I want is if the download failed the program must retry the connection or remove the unfinished file and then try again. I prefer to use C libraries rather than C++ libs. Here is the code I am using:
//lib for curl
#include <curl/curl.h>
#define CURL_STATICLIB
bool downloader3(string url, string file_path) {
CURL *curl;
FILE *fp;
CURLcode res;
curl = curl_easy_init();
if (curl) {
fp = fopen(file_path.c_str(), "wb");
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
res = curl_easy_perform(curl);
//always cleanup
curl_easy_cleanup(curl);
fclose(fp);
double val;
res = curl_easy_getinfo(curl, CURLINFO_SPEED_DOWNLOAD, &val);
if ((CURLE_OK == res) && (val>0))
printf("Average download speed: %0.3f kbyte/sec.\n", val / 1024);
if ((res == CURLE_OK)) {
printf("Download Successful!\r\n");
return true;
}
else {
printf("Downlaod Failed!\r\n");
remove(file_path.c_str()); //remove the temp file
return false;
}
}
}
EDIT---
Thanks to Ring Ø answer. I modifed the code but I am looking for a resume capability that can resume the download of incomplete file.
bool downloader3(string url, string file_path) {
CURL *curl;
FILE *fp = NULL;
CURLcode res;
int status;
int maxtries = 3;
do {
printf("Doing try # %d\r\n", maxtries);
curl = curl_easy_init();
if (curl) {
fp = fopen(file_path.c_str(), "wb");
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10L); // 30 seconds
res = curl_easy_perform(curl);
//always cleanup
curl_easy_cleanup(curl);
fclose(fp);
if ((res == CURLE_OK)) {
printf("Download Successful!\r\n");
break;
//return true;
}
}
} while (--maxtries);
if (maxtries) { // was OK
//curl_easy_cleanup(curl); // clean curl / delete file?
//fclose(fp);
return true;
}
else {
printf("Download Failed!\r\n");
printf("file path is: %s", file_path.c_str());
Sleep(5000);
status = remove(file_path.c_str()); //remove the unfinished file
if (status == 0)
printf("%s file deleted successfully.\n", file_path);
else
{
printf("Unable to delete the file\n");
}
return false;
}
}
You could set a timeout option
curl_easy_setopt(curl, CURLOPT_TIMEOUT, 30L); // 30 seconds
if the operation is not done within 30 seconds, the timeout is triggered. Then check the result value, in a while loop for instance
res = curl_easy_perform( ... );
if (res == CURLE_OK) {
break;
}
// delete file
// keep retrying (add a counter if necessary)
See also the curl page.
Loop example
int maxtries = 5;
do {
curl = curl_easy_init();
if (curl) {
...
res = curl_easy_perform( ... );
if (res == CURLE_OK) {
break;
}
// delete file, curl cleanup...
}
} while ( --maxtries );
if (maxtries) { // was OK
// clean curl / delete file?
}
This is not the ideal solution, as you said, the download may take more or less time. This (should) prevent a never ending program, provided the timeout is big enough.
Curl library was known to have some problems in case of erratic connection - there could be something better nowadays, please try the latest stable build.
If you don't get a better answer within a few days, try to add a "Bounty" of 50 rep to attract more attention.
What you are looking for is the RESUME_FROM feature. To use this you must know which byte you want to start the download from. In this example it is an upload but should be same setopt technique. Here is example usage from curl website:
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com");
/* resume upload at byte index 200 */
curl_easy_setopt(curl, CURLOPT_RESUME_FROM, 200L);
/* ask for upload */
curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
/* set total data amount to expect */
curl_easy_setopt(curl, CURLOPT_INFILESIZE, size_of_file);
/* Perform the request */
curl_easy_perform(curl);
}
source: https://curl.haxx.se/libcurl/c/CURLOPT_RESUME_FROM.html
I am using this code to retrieve the data from the web browser using curl request in c language. I want to store the output in another file or buffer.
#include <stdio.h>
#include <curl/curl.h>
#include <curl/easy.h>
int main(void)
{
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
/* example.com is redirected, so we tell libcurl to follow redirection */
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
/* Perform the request, res will get the return code */
res = curl_easy_perform(curl);
/* Check for errors */
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
/* always cleanup */
curl_easy_cleanup(curl);
}
return 0;
}
The output of this code is an html file. I want to store that html in another file or buffer. How to do that.
Thank you in advance.
Here's a modification to your code that writes the HTML response to a file:
#include <stdio.h>
#include <curl/curl.h>
#include <curl/easy.h>
int main(void)
{
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
/* example.com is redirected, so we tell libcurl to follow redirection */
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
/* create an output file and prepare to write the response */
FILE *output_file = fopen("output_file.html", "w");
curl_easy_setopt(curl, CURLOPT_WRITEDATA, output_file);
/* Perform the request, res will get the return code */
res = curl_easy_perform(curl);
/* Check for errors */
if(res != CURLE_OK) {
fprintf(stderr, "curl_easy_perform() failed: %sn",
curl_easy_strerror(res));
}
/* always cleanup */
curl_easy_cleanup(curl);
}
return 0;
}
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