undefined reference to `pthread_join'解决办法

root@wl-Lenovo-B590:/myworkspace/anvancdedprogramminginunix/mysourcecode/chapter11# gcc pthread_join.c -o pthread_join
/tmp/ccWSGngH.o: In function `main':
pthread_join.c:(.text+0x67): undefined reference to `pthread_create'
pthread_join.c:(.text+0x8b): undefined reference to `pthread_create'
pthread_join.c:(.text+0x9f): undefined reference to `pthread_join'
pthread_join.c:(.text+0xb3): undefined reference to `pthread_join'
collect2: ld 返回 1

问题原因：
pthread 库不是 Linux 系统默认的库，连接时需要使用静态库 libpthread.a，所以在使用pthread_create()创建线程，以及调用 pthread_atfork()函数建立fork处理程序时，需要链接该库。

问题解决：
在编译中要加 -lpthread参数
gcc thread.c -o thread -lpthread

root@wl-Lenovo-B590:/myworkspace/anvancdedprogramminginunix/mysourcecode/chapter11# gcc pthread_join.c -o pthread_join -lpthread
root@wl-Lenovo-B590:/myworkspace/anvancdedprogramminginunix/mysourcecode/chapter11# ./pthread_join 
thread2 return with 2
thread1 return with 1
thread1 exit with1
thread2 exit with2
root@wl-Lenovo-B590:/myworkspace/anvancdedprogramminginunix/mysourcecode/chapter11# 

ok了～～