Hello everyone, I would like your help to decide which is the best way
to download a file in C++, if any of the three forms below, or if you
know any better.
1) using *fork* and *execl* to _execute a program_ (working)
-----
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
// $ g++ download.cpp
// $ ./a.out
int main(int argc, char **argv) {
pid_t child = 0;
int pipes[2];
if(pipe( pipes ) != 0) {
fprintf( stderr, "cannot create pipe" );
return 1;
}
child = fork();
if (child < 0) {
fprintf( stderr, "process failed to fork\n" );
return 1;
}
if (child == 0) {
close(pipes[1]);
// read from pipes[0] here
// wait(NULL);
}
else {
dup2(pipes[1], 0); // 0 is stdout
close(pipes[0]);
system("echo -n 'Start Download'");
execl("/usr/bin/aria2c", "aria2c
","http://curl.haxx.se/download/curl-7.21.4.tar.bz2";, (char *)0); use
aria2c or axel or wget or curl
system("echo -n 'Download Finish'"); // this
line will never execute
}
return 0;
}
-----
2) using a _library_: *curl* (working)
-----
#define CURL_STATICLIB
#include <stdio.h>
#include <curl/curl.h>
#include <curl/types.h>
#include <curl/easy.h>
#include <string>
// sudo aptitude install libcurl3 libcurl3-dev or
http://curl.haxx.se/download.html
// g++ -Wall -std=c++98 -pedantic -Werror -lcurl -I /usr/local/include
-L /usr/local/lib
size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
size_t written;
written = fwrite(ptr, size, nmemb, stream);
return written;
}
int main(void) {
CURL *curl;
FILE *fp;
CURLcode res;
const char *url = "http://curl.haxx.se/download/curl-7.21.4.tar.bz2";;
const char outfilename[FILENAME_MAX] = "curl-7.21.4.tar.bz2";
curl = curl_easy_init();
if (curl) {
fp = fopen(outfilename,"wb");
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
fclose(fp);
}
return 0;
}
-----
3) using *connect* ... *websock* (this algorithm is not working)
-----
struct sockaddr_in webaddress;
int websock;
webaddress.sin_family = AF_INET;
webaddress.sin_addr.s_addr = inet_addr("http://www.google.com/index.html";);
webaddress.sin_port = htons(80);
if(connect(websock, (struct sockaddr *) &webaddress, sizeof(webaddress))
< 0) {
perror("Failed to connect with the server \n");
// TODO: printf or send msg back, or just create blank file
}
// Try to read from website, give error if not possible
//else if(( received = recv(websock,buffer,BUFFSIZE-1, 0)) < 0 )
else if(( received = read(websock,buffer,BUFFSIZE-1)) < 0 ) {
perror("Failed to receive additional bytes from client \n");
}
// Read successful
else if(received > 0) {
printf("Received from Client : %s", buffer);
memset(buffer, 0, sizeof(buffer));
}
// Close the client if badness occurred
else if(received < 1) {
printf("Closing this client (1)\n");
close(websock);
//pthread_exit(NULL);
}
// attempt download index.html
// send file back
// save file to local directory
-----
4) or if you know any better...
Thank you.
John
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