For beginners of C Programming in linux, the problems encountered by programming a url Decoding Program

For beginners of C Programming in linux, If You Want To compile a url Decoding program, you may encounter the following problems: Linux general technology-Linux programming and kernel information. Problem Background: fedora 10 is currently used. Every time a resource is downloaded from CSDN, if the file name of the resource is Chinese, the file name becomes garbled when downloaded to the hard disk. The od tool can be encoded. The "echo" string to be encoded "| od-t x1" command has confirmed that the garbled characters are url encoded. However, the url Decoding tool cannot be found. So I want to get started with C Programming in Linux. The following are two questions you want to answer:
I. Is there a url Decoding tool in Linux?

2. If you want to use the curl_easy_unescape function in C Programming, you have found the header file for declaring this function in the system, however, I cannot find the source code file implementing this function and the compiled so library file for my own program to link. How can I obtain the source file and the so file?