Tribblix: manual page: CURLOPT

CURLOPT_ERRORBUFFER(3) Introduction to Library Functions

NAME

CURLOPT_ERRORBUFFER - error buffer for error messages

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ERRORBUFFER, char *buf);

DESCRIPTION

Pass a char pointer to a buffer that libcurl may use to store human
readable error messages on failures or problems. This may be more
helpful than just the return code from curl_easy_perform(3) and
related functions. The buffer must be at least CURL_ERROR_SIZE bytes
big.

You must keep the associated buffer available until libcurl no longer
needs it. Failing to do so might cause odd behavior or even crashes.
libcurl might need it until you call curl_easy_cleanup(3) or you set
the same option again to use a different pointer.

Do not rely on the contents of the buffer unless an error code was
returned. Since 7.60.0 libcurl initializes the contents of the error
buffer to an empty string before performing the transfer. For earlier
versions if an error code was returned but there was no error detail
then the buffer was untouched.

Do not attempt to set the contents of the buffer yourself, including
in any callbacks you write that may be called by libcurl. The library
may overwrite the buffer after your callback returns.

Consider CURLOPT_VERBOSE(3) and CURLOPT_DEBUGFUNCTION(3) to better
debug and trace why errors happen.

Using this option multiple times makes the last set pointer override
the previous ones. Set it to NULL to disable its use again.

DEFAULT

NULL

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

#include <string.h> /* for strlen() */
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode result;
char errbuf[CURL_ERROR_SIZE];

curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

/* provide a buffer to store errors in */
curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, errbuf);

/* set the error buffer as empty before performing a request */
errbuf[0] = 0;

/* perform the request */
result = curl_easy_perform(curl);

/* if the request did not complete correctly, show the error
information. if no detailed error information was written to errbuf
show the more generic information from curl_easy_strerror instead.
*/
if(result != CURLE_OK) {
size_t len = strlen(errbuf);
fprintf(stderr, "\nlibcurl: (%d) ", result);
if(len)
fprintf(stderr, "%s%s", errbuf,
((errbuf[len - 1] != '\n') ? "\n" : ""));
else
fprintf(stderr, "%s\n", curl_easy_strerror(result));
}
}
}

AVAILABILITY

Added in curl 7.1

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).