LibCurl undefined references - c

Question

Trying to make a translation program in C using Libcurl. Text editor is Atom and using gnu compiler.
When compiling as "gcc example.c" i get these errors:
Navid#LAPTOP-ASS7BGNB /c/users/navid/desktop/Lipcurl/libcurl-sample-master/curl
$ gcc projektzwei.c
C:\Users\Navid\AppData\Local\Temp\ccwZwaAr.o:projektzwei.c:(.text+0xa18): undefined reference to `_imp__curl_easy_init'
C:\Users\Navid\AppData\Local\Temp\ccwZwaAr.o:projektzwei.c:(.text+0xa4a): undefined reference to `_imp__curl_easy_setopt'
C:\Users\Navid\AppData\Local\Temp\ccwZwaAr.o:projektzwei.c:(.text+0xa83): undefined reference to `_imp__curl_easy_setopt'
C:\Users\Navid\AppData\Local\Temp\ccwZwaAr.o:projektzwei.c:(.text+0xa90): undefined reference to `_imp__curl_easy_perform'
C:\Users\Navid\AppData\Local\Temp\ccwZwaAr.o:projektzwei.c:(.text+0xaa6): undefined reference to `_imp__curl_easy_strerror'
C:\Users\Navid\AppData\Local\Temp\ccwZwaAr.o:projektzwei.c:(.text+0xacf): undefined reference to `_imp__curl_easy_cleanup'
collect2.exe: error: ld returned 1 exit status
And when compiling as "gcc projektzwei.c -lcurl" i get this error:
Navid#LAPTOP-ASS7BGNB /c/users/navid/desktop/Lipcurl/libcurl-sample-master/curl
$ gcc projektzwei.c -lcurl
c:/mingw/bin/../lib/gcc/mingw32/6.3.0/../../../../mingw32/bin/ld.exe: cannot find -lcurl
collect2.exe: error: ld returned 1 exit status
This is my code
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "stdafx.h"
#include "libcurl/include/curl/curl.h"
#ifdef _DEBUG
#pragma comment(lib, "libcurl/lib/libcurl_a_debug.lib")
#else
#pragma comment(lib, "libcurl/lib/libcurl_a.lib")
#endif
#define TEXT_MAX 2000
#define CANDIDAT_INPUT 2 /*Amount of valid inputs for candidat*/
#define PARTY_INPUT 14 /*Amount of valid inputs for parties*/
void prepare_files(char *Key);
void Introduction(int Sprog);
void Assemble_URL_To_Translate(int Sprog, FILE *fp);
char *create_URL(char Key[], char Source[], char Target[], char Message[]);
const char *chosen_language(int Target);
int valid_input_checker(const char **index, int array_lenght, char input[]);
void create_message(FILE *fp, char *Message);
void fil_print(FILE *fp);
void Partier(char input[], int Sprog, char chosen_party[]);
const char *chosen_party(char parti_input[]);
void Candidat_Exist(char parti_input[], int Sprog, char chosen_party[]);
char *delete_space(char text[]);
void match_and_insert(int(*str_pred)(char*), char str[], int str_in_len, const char *prefix, char str_out[], int str_out_len);
int space_detector(char* cp);
void translator(void);
int main(void)
{
int Sprog;
/*User is asked to choose language*/
printf("Choose language:\n"
"(1) Dansk\n(2) English\n(3) Turk\n(4) Polski\n(5) Alearabia"
"\n(6) Deutsch\n(7) Kurdi\n(8) Romanesc\n(9) Bosanski\n(10) Soomaali\n");
scanf("%d", &Sprog);
Introduction(Sprog); /*Initializes the program with the given language*/
return 0;
}
void prepare_files(char *Key)
{
FILE *fp;
fp = fopen("API.txt", "r");
if (fp == NULL)
{
printf("Filen kunne ikke �bnes.\n");
exit(EXIT_FAILURE);
}
while (!feof(fp))
{
fscanf(fp, "%s", Key);
}
}
void Assemble_URL_To_Translate(int Sprog, FILE *fp)
{
/*laver api key, target, message og url*/
char SOURCE[5] = "da";
char TARGET[5];
char MESSAGE[TEXT_MAX];
char KEY[100];
char URL[TEXT_MAX];
URL[0] = '\0';
prepare_files(KEY);
strcpy(TARGET, chosen_language(Sprog));
create_message(fp, MESSAGE);
fp = fopen("Translate_Input.txt", "w");
strcat(URL, create_URL(KEY, SOURCE, TARGET, MESSAGE));
fprintf(fp, "%s", URL);
fil_print(fp);
}
void Introduction(int Sprog)
{
/*Function to print introduction at the chosen language and ask the user what their next move is.*/
FILE *fp;
char parti_input[5]; /*Array for user input*/
const char *valid_inputs[PARTY_INPUT] = { "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "b" }; /*All the valid input options in the scanf*/
char party[50]; /*Array to store the string containing what party has been chosen*/
/*This will be replaced when we got a translator function.*/
fp = fopen("Introduktion.txt", "r");
Assemble_URL_To_Translate(Sprog, fp);
translator();
do /*Asks the user to tell us what party they want to have a look at or optionally, go back.*/
{
printf("Press:\n"
"(1) Alternativet\n(2) Det Konversative Folkeparti\n(3) DF\n(4) Enhedslisten\n"
"(5) Fjordlisten\n(6) Kristendemokraterne\n(7) Liberal Alliance\n(8) Nationalpartiet\n"
"(9) Nye Borgerlige\n(10) Radikale Venstre\n(11) SF\n(12) Socialdemokraterne\n(13) Venstre\n"
"(b) for at gaa tilbage\n");
scanf("%s", &parti_input);
}
while (valid_input_checker(valid_inputs, PARTY_INPUT, parti_input) == 0);
if (strchr(parti_input, 'b') != NULL)
{
main();
}
else
{
strcpy(party, chosen_party(parti_input));
Partier(parti_input, Sprog, party);
}
}
char *create_URL(char Key[], char Source[], char Target[], char Message[])
{
char URL[TEXT_MAX] = "https://www.googleapis.com/language/translate/v2?key=&source=&target=&q=";
char *URLptr = URL;
sprintf(URL, "https://www.googleapis.com/language/translate/v2?key=%s&source=%s&target=%s&q=", Key, Source, Target);
Message = delete_space(Message);
strcat(URL, Message);
return URLptr;
}
const char *chosen_language(int Target)
{
/*Finds out what party has been chosen and returns it as a string.*/
const char *sprog[] = { "da", "en", "tr", "pl", "ar", "de", "ku", "ro", "bs", "so" };
return sprog[Target - 1]; /*-1 cause array index starts at 0, but the users lowest valid input is 1*/
}
const char *chosen_party(char parti_input[])
{
/*Finds out what party has been chosen and returns it as a string.*/
int input_tal = atoi(parti_input);
const char *partier[] = { "Alternativet", "Det_Konversative_Folkeparti", "DF", "Enhedslisten"
,"Fjordlisten", "Kristendemokraterne", "Liberal_Alliance", "Nationalpartiet"
,"Nye_Borgerlige", "Radikale_Venstre", "SF", "Socialdemokraterne", "Venstre" };
return partier[input_tal - 1]; /*-1 cause array index starts at 0, but the users lowest valid input is 1*/
}
int valid_input_checker(const char **index, int array_lenght, char input[])
{
/*Algoritme to find out if the entered input from the user is valid.*/
for (int i = 0; i < array_lenght; i++)
{
if (strcmp(index[i], input) == 0) /*If we find a match, we return 1*/
{
return 1;
}
else if (i == array_lenght && (strcmp(index[i], input) != 0)) /*If we have been through the entire index og valid input without a match, we return 0*/
{
return 0;
}
}
return 0;
}
void create_message(FILE *fp, char *Message)
{
int ch;
int i = 0;
while ((ch = fgetc(fp)) != EOF)
{
Message[i] = ch;
i++;
}
Message[i] = '\0';
fclose(fp); /*As soon as we are done with the file we close it. ALWAYS do this.*/
}
void fil_print(FILE *fp)
{
/*Simple algoritme to print a file.*/
int ch;
int i = 0;
char str[400]; /*Array where the file is getting stored*/
while ((ch = fgetc(fp)) != EOF)
{
str[i] = ch;
i++;
}
str[i] = '\0';
//printf("%s\n", str); /*Prints the file*/
fclose(fp); /*As soon as we are done with the file we close it. ALWAYS do this.*/
}
void Partier(char parti_input[], int Sprog, char chosen_party[])
{
/*Function to print the overview of what the chosen party stands for and gives the user the option to view the candidats or go back.*/
FILE *fp;
char kandidat_input[5]; /*This is the input we get from the user, which tells us whether they user wants to look at candidats for the party, og go back.*/
const char *valid_inputs[CANDIDAT_INPUT] = { "1", "b" }; /*Array of valid inputs for the scanf*/
char party_intro[50]; /*Array to store the path for the party overview file.*/
sprintf(party_intro, "Partier/%s/M�rkesager.txt", chosen_party); /*Stores the path*/
printf("party: %s\n", party_intro); /*Nice to have, not necessary. Tells you what path it is going to print from.*/
fp = fopen(party_intro, "r"); /*Opens the file at the given path*/
fil_print(fp); /*Prints the file*/
do/*User is asked to tell what their next move is*/
{
printf("tryk:\n"
"(1) Se partiets kandidater\n");
printf("(b) for at gaa tilbage\n");
scanf("%s", &kandidat_input);
}
while (valid_input_checker(valid_inputs, CANDIDAT_INPUT, kandidat_input) == 0); /*We have a function 'valid_input_checker' which returns either 1 or 0. If 1,
the users input was valid and the program will proceed. If 0, the input was incorrect
and the user is asked again to type something.*/
if (strchr(kandidat_input, 'b') != NULL) /*Checks if the input was 'b'*/
{
Introduction(Sprog);
}
else
Candidat_Exist(parti_input, Sprog, chosen_party);
}
void Candidat_Exist(char parti_input[], int Sprog, char chosen_party[])
{
/*Prints every single candidat for the given party.*/
FILE *fp;
char user_input[5];
char candidattxt[50]; /*Array to later store the string used to open the candidat text file in fopen.*/
char path[40]; /*Array to tell your computer where it is going to find the text file.*/
sprintf(path, "Partier/%s/Kandidat_\0", chosen_party); /*Takes the users chosen party and adds it to the path, to determine where we are going to find the text files.*/
int size = 2;
/*Algoritme to check if the next candidat exist and will print it if it does. If it exist, the 'size' is incremented by 1, so we keep cycling through the list of
candidats. If it doesn't, we break.*/
for (int i = 1; i < size; i++)
{
sprintf(candidattxt, "%s%d.txt", path, i); /*All candidates are saved as "Kandidat_X" where X is an integer starting at 1. We finish the path by specifying what
file want to check.*/
fp = fopen(candidattxt, "r"); /*Opens the candidats text file*/
if (fp != NULL) /*Checks if the file exist*/
{
/*printf("candi: %s\n", candidattxt); Command to show you what candidat is getting printet*/
fil_print(fp);
fclose(fp);
size++;
}
else if (fp == NULL)
{
break;
}
}
do/*User is asked to tell what their next move is*/
{
printf("tryk:\n(b) for at gaa tilbage\n");
scanf("%s", &user_input);
}
while (strcmp(user_input, "b") != 0); /*We have a function 'valid_input_checker' which returns either 1 or 0. If 1,
the users input was valid and the program will proceed. If 0, the input was incorrect
and the user is asked again to type something.*/
Partier(parti_input, Sprog, chosen_party);
}
char *delete_space(char text[])
{
char str_res[TEXT_MAX];
char *str_res_ptr = str_res;
int i, j, k;
/* Initialize str_res til zero */
for (i = 0; i < TEXT_MAX; ++i)
str_res[i] = '\0';
printf("len: %d\n", strlen(text));
match_and_insert(space_detector, text, 200, "%20", str_res, TEXT_MAX);
for (j = 0, k = 0; j < 200; j++)
{
str_res[j - k] = str_res[j];
if (str_res[j] == ' ')
k++;
}
str_res[j] = '\0';
return str_res_ptr;
}
void match_and_insert(int(*str_pred)(char*), char str[], int str_in_len, const char *prefix, char str_out[], int str_out_len)
/*Shoutout til Kurt N�rmark*/
{
int i = 0, o = 0;
while (i < str_in_len)
{
int match_result = str_pred(str + i);
if (match_result > 0)
{
strcpy(str_out + o, prefix);
o += strlen(prefix);
strncpy(str_out + o, str + i, match_result);
i += match_result; o += match_result;
}
else if (match_result == 0)
{
str_out[o++] = str[i++];
}
else
{
printf("Should not happen!\n");
exit(EXIT_FAILURE);
}
}
}
int space_detector(char* cp)
{
int result = isspace(cp[0]);
if (result)
return 1;
else
return 0;
}
void translator(void)
{
CURL *curl;
CURLcode res;
int ch, i = 0;
char Message[2000];
FILE *fp2;
fp2 = fopen("Translate_Input.txt", "r");
while ((ch = fgetc(fp2)) != EOF)
{
Message[i] = ch;
i++;
}
Message[i] = '\0';
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_URL, Message);
FILE *fp = fopen("target.txt", "w");
curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
/* Perform the request, res will get the return code */
res = curl_easy_perform(curl);
/* Check for errors */
if (res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
/* always cleanup */
curl_easy_cleanup(curl);
fclose(fp);
}
}
I've searched around a bit and it seems most people get it fixed by adding the
-lcurl at the end of the gcc command but it just doesn't work for me. Any ideas?

Answer 1

Based on this line:
#include "libcurl/include/curl/curl.h"
it looks like you've not installed curl on your machine, you've just downloaded the source and compiled it. That's not the wrong way to do it, but it does make your life more difficult.
Firstly you need to correct the above line as it should be
#include <curl/curl.h>
You then need to tell the compiler where the include files are by adding "-Ilibcurl/include". By doing this, it means that if/when you install libcurl properly, you won't need to make any changes to your code - you can just remove the -I option.
Secondly, you also need to tell the compiler (technically the linker) where the libraries are with the -L option. It looks like that should be "-Llibcurl/lib/"
So to summarise, having fixed the include line as per above, your command to compile your code should look like:
gcc -Ilibcurl/include -Llibcurl/lib projektzwei.c -lcurl