《linux程序设计》线程

Question

最近看《linux程序设计》用信号量同步线程遇到疑惑了
代码说明：main线程接收一个字符串
t线程检测字符串的长度

 #include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<pthread.h>
#include<semaphore.h>
void *thread_function(void*arg);
sem_t bin_sem;
#define WORK_SIZE 1024
char work_area[WORK_SIZE];
void test(int res,char*s)
{
    if(res!=0)
    {
        fprintf(stderr,"%s failed\n",s);
        exit(1);
    }
}
int main()
{
    int res;
    pthread_t t;
    void *thread_result;
    res=sem_init(&bin_sem,0,0);
    test(res,"sem_init");
    res=pthread_create(&t,NULL,thread_function,NULL);
    test(res,"pthread_creat");
    printf("Input your word(end to quit)\n");
    while(strncmp("end",work_area,3)!=0)
    {
        if(strncmp(work_area,"FAST",4)==0)
        {
            sem_post(&bin_sem);
            sleep(1);
            strcpy(work_area,"xxxx");/*疑问在这里*/
            printf("work_area: %s\n",work_area);
            sleep(1);
        }else
            fgets(work_area,WORK_SIZE,stdin);
        sem_post(&bin_sem);
        sleep(1);
    }
    printf("\nWaiting for thread to finish...\n");
    res=pthread_join(t,&thread_result);
    test(res,"pthread_join");
    printf("Thread joined\n");
    sem_destroy(&bin_sem);
    exit(0);
}
void *thread_function(void*arg)
{
    sem_wait(&bin_sem);
    while(strncmp("end",work_area,3)!=0)
    {
        printf("You input %d character\n",strlen(work_area)-1);
        sem_wait(&bin_sem);

    }
    pthread_exit(NULL);
}

cser@cser:./thread2
Input your word(end to quit)
FAST(我输入的）
you input 4 character
you input 4 character
work_area: xxxx
you input 3 character
cser@cser:
我就是最后那个输出不明白，为什么会是3而不是4，
如果我strcpy(work_area,"xxxxx"),则最后会输出4，
不明白最后输出的总比字符长度少1？为什么？
恳请不吝赐教

Answer 1

printf("You input %d character\n",strlen(work_area)-1);

strlen(work_area)-1);