gcc complie pthread

#ifndef __errors_h

#define __errors_h

#include <unistd.h>

#include <errno.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

/*

 * Define a macro that can be used for diagnostic output from

 * examples. When compiled -DDEBUG, it results in calling printf

 * with the specified argument list. When DEBUG is not defined, it

 * expands to nothing.

 */

#ifdef DEBUG

# define DPRINTF(arg) printf arg

#else

# define DPRINTF(arg)

#endif

/*

 * NOTE: the "do {" ... "} while (0);" bracketing around the macros

 * allows the err_abort and errno_abort macros to be used as if they

 * were function calls, even in contexts where a trailing ";" would

 * generate a null statement. For example,

 *

 *      if (status != 0)

 *          err_abort (status, "message");

 *      else

 *          return status;

 *

 * will not compile if err_abort is a macro ending with "}", because

 * C does not expect a ";" to follow the "}". Because C does expect

 * a ";" following the ")" in the do...while construct, err_abort and

 * errno_abort can be used as if they were function calls.

 */

#define err_abort(code,text) do { \

    fprintf (stderr, "%s at \"%s\":%d: %s\n", \

        text, __FILE__, __LINE__, strerror (code)); \

    abort (); \

    } while (0)

#define errno_abort(text) do { \

    fprintf (stderr, "%s at \"%s\":%d: %s\n", \

        text, __FILE__, __LINE__, strerror (errno)); \

    abort (); \

    } while (0)

#endif

/*

 * alarm_thread.c

 *

 * This version of alarm.c uses pthread_create to create a

 * separate thread to wait for each alarm to expire.

 */

#include <pthread.h>

#include "errors.h"

typedef struct alarm_tag {

    int         seconds;

    char        message[64];

} alarm_t;

void *alarm_thread (void *arg)

{

    alarm_t *alarm = (alarm_t*)arg;

    int status;

    status = pthread_detach (pthread_self ());

    if (status != 0)

        err_abort (status, "Detach thread");

    sleep (alarm->seconds);

    printf ("(%d) %s\n", alarm->seconds, alarm->message);

    free (alarm);

    return NULL;

}

int main (int argc, char *argv[])

{

    int status;

    char line[128];

    alarm_t *alarm;

    pthread_t thread;

    while (1) {

        printf ("Alarm> ");

        if (fgets (line, sizeof (line), stdin) == NULL) exit (0);

        if (strlen (line) <= 1) continue;

        alarm = (alarm_t*)malloc (sizeof (alarm_t));

        if (alarm == NULL)

            errno_abort ("Allocate alarm");

        /*

         * Parse input line into seconds (%d) and a message

         * (%64[^\n]), consisting of up to 64 characters

         * separated from the seconds by whitespace.

         */

        if (sscanf (line, "%d %64[^\n]", 

            &alarm->seconds, alarm->message) < 2) {

            fprintf (stderr, "Bad command\n");

            free (alarm);

        } else {

            status = pthread_create (

                &thread, NULL, alarm_thread, alarm);

            if (status != 0)

                err_abort (status, "Create alarm thread");

        }

    }

}

http://unix.stackexchange.com/questions/33396/gcc-cant-link-to-pthread

gcc alarm_thread.c -lpthread

gcc -pthread pthread_sample.c