125 lines
3.5 KiB
Markdown
125 lines
3.5 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_POSTFIELDS
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_COPYPOSTFIELDS (3)
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- CURLOPT_MIMEPOST (3)
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- CURLOPT_POSTFIELDSIZE (3)
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- CURLOPT_READFUNCTION (3)
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- CURLOPT_UPLOAD (3)
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---
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# NAME
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CURLOPT_POSTFIELDS - data to POST to server
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POSTFIELDS, char *postdata);
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~~~
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# DESCRIPTION
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Pass a char pointer as parameter, pointing to the data buffer to use in an
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HTTP POST operation. The data must be formatted and encoded the way you want
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the server to receive it. libcurl does not convert or encode it in any
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way. For example, the web server may assume that this data is URL encoded.
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The data pointed to is NOT copied by the library: as a consequence, it must be
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preserved by the calling application until the associated transfer finishes.
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This behavior can be changed (so libcurl does copy the data) by instead using
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the CURLOPT_COPYPOSTFIELDS(3) option.
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This POST is a normal **application/x-www-form-urlencoded** kind (and
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libcurl sets that Content-Type by default when this option is used), which is
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commonly used by HTML forms. Change Content-Type with
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CURLOPT_HTTPHEADER(3).
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You can use curl_easy_escape(3) to URL encode your data, if
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necessary. It returns a pointer to an encoded string that can be passed as
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*postdata*.
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Using CURLOPT_POSTFIELDS(3) implies setting CURLOPT_POST(3) to 1.
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If CURLOPT_POSTFIELDS(3) is explicitly set to NULL then libcurl gets the
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POST data from the read callback. If you want to send a zero-byte POST set
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CURLOPT_POSTFIELDS(3) to an empty string, or set CURLOPT_POST(3)
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to 1 and CURLOPT_POSTFIELDSIZE(3) to 0.
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libcurl assumes this option points to a null-terminated string unless you also
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set CURLOPT_POSTFIELDSIZE(3) to specify the length of the provided data,
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which then is strictly required if you want to send off null bytes included in
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the data.
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Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header,
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and libcurl adds that header automatically if the POST is either known to be
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larger than 1MB or if the expected size is unknown. You can disable this
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header with CURLOPT_HTTPHEADER(3) as usual.
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To make **multipart/formdata** posts, check out the
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CURLOPT_MIMEPOST(3) option combined with curl_mime_init(3).
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# DEFAULT
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NULL
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# PROTOCOLS
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HTTP
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# EXAMPLE
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~~~c
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/* send an application/x-www-form-urlencoded POST */
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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const char *data = "data to send";
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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/* size of the POST data if strlen() is not good enough */
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curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, 12L);
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/* pass in a pointer to the data - libcurl does not copy */
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curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);
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curl_easy_perform(curl);
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}
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/* send an application/json POST */
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curl = curl_easy_init();
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if(curl) {
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const char *json = "{\"name\": \"daniel\"}";
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struct curl_slist *slist1 = NULL;
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slist1 = curl_slist_append(slist1, "Content-Type: application/json");
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slist1 = curl_slist_append(slist1, "Accept: application/json");
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/* set custom headers */
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curl_easy_setopt(curl, CURLOPT_HTTPHEADER, slist1);
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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/* pass in a pointer to the data - libcurl does not copy */
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curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json);
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curl_easy_perform(curl);
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}
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}
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~~~
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# AVAILABILITY
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Always
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# RETURN VALUE
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Returns CURLE_OK
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