Help with pthread

[curi]

Hi, I'm working on an application of C programming language. I want to build a code that uses multitasking; at the moment I'm just experimenting with examples I got from books and WEBside. Many of them use pthread_create () to create a thread. I don't know why, but my compiler prints an error message that says: ".../home/investigacion/ejpthread/src/ejpthread.c:62: undefined reference to `pthread_create'". First I though it was because I didn't include the respective header (pthread.h), but even after I wrote a code line including it, the message was printed again every time I compiled my code.
Inspired in an example I found in a book of Linux programming, I wrote following code:
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>


void *child_fn (void *arg);

int main (void)
{

pthread_t tchild;
int algo;
algo = pthread_create (&tchild, NULL, &child_fn, NULL );
if (algo != 0)
perror ("Pthreads error");

pthread_join (tchild, NULL);
return 0;
}

void *child_fn (void *arg)
{

puts ("Soy un thread hijo"); //This is spanish "I'm a thread child"
return NULL;
}

Similarly occurs with function pthread_join(); compiler returns ERROR.
I'll appreciate your help. Thanks!

[HCastillo]

Hi, I'm working on an application of C programming language. I want to build a code that uses multitasking; at the moment I'm just experimenting with examples I got from books and WEBside. Many of them use pthread_create () to create a thread. I don't know why, but my compiler prints an error message that says: ".../home/investigacion/ejpthread/src/ejpthread.c:62: undefined reference to `pthread_create'". First I though it was because I didn't include the respective header (pthread.h), but even after I wrote a code line including it, the message was printed again every time I compiled my code.
Inspired in an example I found in a book of Linux programming, I wrote following code:
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>


void *child_fn (void *arg);

int main (void)
{

pthread_t tchild;
int algo;
algo = pthread_create (&tchild, NULL, &child_fn, NULL );
if (algo != 0)
perror ("Pthreads error");

pthread_join (tchild, NULL);
return 0;
}

void *child_fn (void *arg)
{

puts ("Soy un thread hijo"); //This is spanish "I'm a thread child"
return NULL;
}

Similarly occurs with function pthread_join(); compiler returns ERROR.
I'll appreciate your help. Thanks!

Is it a compiler or linker error. Compiling should have no problem if you have the header files but you will have to add "-lpthread" or something similar to you linking options. For example: gcc -o foo foo.c -lpthread

[curi]

¡Muchisimas gracias! A lot of thanks!!!!

That's what I needed; I have alredy tried, and it worked!