Extracting information from a URI

I'm completely new to C and my first project is to create a simple cURL-like HTTP request client... but first, I need to create a function that can parse a URL. I've created this function, and it seems to work quite well, but since I'm so new to the complexities of C, can someone check for any errors or to see if I can improve clock efficiency?

Example usage can be found here.

```
#include
#include
#include

void filterURLstring(char *weburl, char protocol, char username, char password, char host, char port, char path);

int main() {
char *text = "http://mhdfffffjddj:abc123@192.168.0.2:8888/servlet/rece/";
char protocol, username, password, host, port, path;
filterURLstring(text, &protocol, &username, &password, &host, &port, &path);
printf("Protocol:\"%s\"\n", protocol);
printf("Username:\"%s\"\n", username);
printf("Password:\"%s\"\n", password);
printf("Host:\"%s\"\n", host);
printf("Port:\"%s\"\n", port);
printf("Path:\"%s\"\n", path);
free(protocol);
free(username);
free(password);
free(host);
free(port);
free(path);
return 0;
}

void filterURLstring(char *weburl, char protocol, char username, char password, char host, char port, char path) {
char postprotocol, postuserinfo, postusername, login, posthost, posthostname, hostloc, postport;
int isPath;
if ((postprotocol = strstr(weburl, "://")) == NULL) {
printf("Input URL is invalid. Exiting...\n");
exit(1);
}
protocol = malloc(sizeof(char) (postprotocol - weburl + 1));
strncpy(*protocol, weburl, postprotocol - weburl);
postprotocol = (postprotocol + (*(postprotocol+3)=='/'?4:3));
if ((postuserinfo = strstr(postprotocol, "@")) != NULL) {
if ((postusername = strchr(postprotocol, ':')) != NULL) {
password = malloc(sizeof(char) (postuserinfo - postusername + 1));
strncpy(*password, postusername + 1, (postuserinfo - postusernam

Think in terms of an Abstract Data Type (ADT)

@x79 is right about using a struct for this.
In fact, it makes sense to think of this in terms of an abstract data type,
as defined in Code Complete:


An abstract data type is a collection of data and operations that work on that data.

The collection of data is the URL info, wrapped in a struct, and the operations can be:

UrlInfo * createUrlInfo(const char *);
deleteUrlInfo(UrlInfo *);
isValidUrlInfo(UrlInfo *);
printUrlInfo(UrlInfo *);

This collection of methods together form an abstract data type.
They encapsulate the operations you need,
while hiding the implementation details.
Users of a UrlInfo don't need to know how the operations work,
they just need to know what the operations are in the ADT (create / delete / isValid / print).
These methods closely collaborate with each other,
emulating class-like behavior in object oriented languages.

Armed with this ADT,
your main function can be rewritten in a more functional, natural way:

int main() {
    const char * text = "http://mhdfffffjddj:abc123@192.168.0.2:8888/servlet/rece/";
    UrlInfo * urlInfo = createUrlInfo(text);
    if (isValidUrlInfo(urlInfo)) {
        printUrlInfo(urlInfo);
    }
    deleteUrlInfo(urlInfo);
}

The purpose of the isValidUrlInfo is to move the exit statement out of the current implementation.
It's not good when a function exits in the middle of the program.
Controlling the program flow is not the job of a function parsing a URL.
The parser should just parse, and let the caller decide what to do with an invalid input.

Other improvements

port make would make sense to store in an int, not a char*

Instead of hardcoding the URL used by the program,
it would be much more useful to take it as a command line argument, for example:

int main(int argc, char ** argv) {
    const char * text = argv[1];
    UrlInfo * urlInfo = createUrlInfo(text);
    if (isValidUrlInfo(urlInfo)) {
        printUrlInfo(urlInfo);
    }
    deleteUrlInfo(urlInfo);
}

No need to do return 0 at the end of main,
the compiler automatically adds that.

This line is too tightly packed:

int userlen = (postusername?postusername:postuserinfo) - postprotocol;

Use spaces around operators to make it more readable, like this:

int userlen = (postusername ? postusername : postuserinfo) - postprotocol;

Suggested implementation

Putting some of the above points together,
a Url Info abstract data type and a main method using it might look like this:

```
#include
#include
#include

typedef struct UrlInfo {
char * protocol;
char * username;
char * password;
char * host;
char * port;
char * path;
} UrlInfo;

UrlInfo createUrlInfo(const char );
void deleteUrlInfo(UrlInfo *);
int isValidUrlInfo(UrlInfo *);
void printUrlInfo(UrlInfo *);

int main(int argc, char ** argv) {
int i;
UrlInfo * urlInfo;
for (i = 1; i protocol = NULL;
urlInfo->username = NULL;
urlInfo->password = NULL;
urlInfo->host = NULL;
urlInfo->port = NULL;
urlInfo->path = NULL;

int isPath;
if ((postprotocol = strstr(weburl, "://")) == NULL) {
return urlInfo;
}
urlInfo->protocol = malloc(sizeof(char) * (postprotocol - weburl + 1));
strncpy(urlInfo->protocol, weburl, postprotocol - weburl);
postprotocol = (postprotocol + (*(postprotocol + 3) == '/' ? 4 : 3));
if ((postuserinfo = strstr(postprotocol, "@")) != NULL) {
if ((postusername = strchr(postprotocol, ':')) != NULL) {
urlInfo->password = malloc(sizeof(char) * (postuserinfo - postusername + 1));
strncpy(urlInfo->password, postusername + 1, (postuserinfo - postusername - 1));
} else {
urlInfo->password = NULL;
}
int userlen = (postusername?postusername:postuserinfo) - postprotocol;
urlInfo->username = malloc(sizeof(char) * userlen + 1);
strncpy(urlInfo->username, postprotocol, userlen);
}
hostloc = (postuserinfo?postuserinfo + 1:postprotocol);
if ((posthost = strchr(hostloc, '/')) == NULL) {
posthost = hostloc + strlen(hostloc);
isPath = 1;
}
if ((posthostname = strchr(hostloc, ':')) == NULL) {
posthostname = posthost;
}
urlInfo->host = malloc(sizeof(char) * (posthostname - hostloc + 1));
strncpy(urlInfo->host, hostloc, (posthostname - hostloc));
if (posthostname != posthost) {
posthostname++;
urlInfo->port = malloc(sizeof(char) * (posthost - posthostname + 1));
strncpy(urlInfo->port, posthostname, (posthost - posthostname));
} else {
urlInfo->port = malloc(sizeof(char) * 2 + 1);
strncpy(urlInfo->port, "80", 2);
}
if (isPath) {
urlInfo->path = malloc(sizeof(char) * strlen(posthost));
strncpy(urlInfo->path, posthost, strlen(posthost));
} else {
urlInfo->path = calloc(1, 1);
}
return urlInfo;
}

void deleteUrlInfo(UrlIn

StackExchange Code Review Q#83822, answer score: 5