curl_easy_unescape (3) Linux Manual Page
curl_easy_unescape – URL decodes the given string
Synopsis
#include <curl/curl.h> char *curl_easy_unescape( CURL *curl, char *url, int inlength , int *outlength );
Description
This function converts the given URL encoded input string to a "plain string" and returns that in an allocated memory area. All input characters that are URL encoded (%XX where XX is a two-digit hexadecimal number) are converted to their binary versions.If the length argument is set to 0 (zero), curl_easy_unescape(3) will use strlen() on the input url string to find out the size.
If outlength is non-NULL, the function will write the length of the returned string in the integer it points to. This allows an escaped string containing %00 to still get used properly after unescaping.
You must curl_free(3) the returned string when you’re done with it.