ftpuploadresume.c
/*************************************************************************** * _ _ ____ _ * Project ___| | | | _ \| | * / __| | | | |_) | | * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * * Copyright (C) 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.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. * * SPDX-License-Identifier: curl * ***************************************************************************/ /* <DESC> * Upload to FTP, resuming failed transfers. Active mode. * </DESC> */ #include <stdlib.h> #include <stdio.h> #include <curl/curl.h> /* parse headers for Content-Length */ static size_t getcontentlengthfunc(void *ptr, size_t size, size_t nmemb, void *stream) { int r; long len = 0; r = sscanf(ptr, "Content-Length: %ld\n", &len); if(r) *((long *) stream) = len; return size * nmemb; } /* discard downloaded data */ static size_t discardfunc(void *ptr, size_t size, size_t nmemb, void *stream) { (void)ptr; (void)stream; return size * nmemb; } /* read data to upload */ static size_t readfunc(char *ptr, size_t size, size_t nmemb, void *stream) { FILE *f = stream; size_t n; if(ferror(f)) return CURL_READFUNC_ABORT; n = fread(ptr, size, nmemb, f) * size; return n; } static int upload(CURL *curlhandle, const char *remotepath, const char *localpath, long timeout, long tries) { FILE *f; long uploaded_len = 0; CURLcode r = CURLE_GOT_NOTHING; int c; f = fopen(localpath, "rb"); if(!f) { perror(NULL); return 0; } curl_easy_setopt(curlhandle, CURLOPT_UPLOAD, 1L); curl_easy_setopt(curlhandle, CURLOPT_URL, remotepath); if(timeout) curl_easy_setopt(curlhandle, CURLOPT_SERVER_RESPONSE_TIMEOUT, timeout); curl_easy_setopt(curlhandle, CURLOPT_HEADERFUNCTION, getcontentlengthfunc); curl_easy_setopt(curlhandle, CURLOPT_HEADERDATA, &uploaded_len); curl_easy_setopt(curlhandle, CURLOPT_WRITEFUNCTION, discardfunc); curl_easy_setopt(curlhandle, CURLOPT_READFUNCTION, readfunc); curl_easy_setopt(curlhandle, CURLOPT_READDATA, f); /* enable active mode */ curl_easy_setopt(curlhandle, CURLOPT_FTPPORT, "-"); /* allow the server no more than 7 seconds to connect back */ curl_easy_setopt(curlhandle, CURLOPT_ACCEPTTIMEOUT_MS, 7000L); curl_easy_setopt(curlhandle, CURLOPT_FTP_CREATE_MISSING_DIRS, 1L); curl_easy_setopt(curlhandle, CURLOPT_VERBOSE, 1L); for(c = 0; (r != CURLE_OK) && (c < tries); c++) { /* are we resuming? */ if(c) { /* yes */ /* determine the length of the file already written */ /* * With NOBODY and NOHEADER, libcurl issues a SIZE command, but the only * way to retrieve the result is to parse the returned Content-Length * header. Thus, getcontentlengthfunc(). We need discardfunc() above * because HEADER dumps the headers to stdout without it. */ curl_easy_setopt(curlhandle, CURLOPT_NOBODY, 1L); curl_easy_setopt(curlhandle, CURLOPT_HEADER, 1L); r = curl_easy_perform(curlhandle); if(r != CURLE_OK) continue; curl_easy_setopt(curlhandle, CURLOPT_NOBODY, 0L); curl_easy_setopt(curlhandle, CURLOPT_HEADER, 0L); fseek(f, uploaded_len, SEEK_SET); curl_easy_setopt(curlhandle, CURLOPT_APPEND, 1L); } else { /* no */ curl_easy_setopt(curlhandle, CURLOPT_APPEND, 0L); } r = curl_easy_perform(curlhandle); } fclose(f); if(r == CURLE_OK) return 1; else { fprintf(stderr, "%s\n", curl_easy_strerror(r)); return 0; } } int main(void) { CURL *curlhandle = NULL; curl_global_init(CURL_GLOBAL_ALL); curlhandle = curl_easy_init(); upload(curlhandle, "ftp://user:pass@example.com/path/file", "C:\\file", 0, 3); curl_easy_cleanup(curlhandle); curl_global_cleanup(); return 0; }
Notice
This source code example is simplified and ignores return
codes and error checks to a large extent. We do this to highlight the libcurl
function calls and related options and reduce unrelated code.
A real-world application will of course properly check every return value and exit correctly at the first serious error.