在 linux的C++的main 函数里面 开一个线程 去定时的执行某个函数

[G_G_Boon]

在 linux的C++的main 函数里面 开一个线程 去定时的执行某个函数，刚接触linux这块，对线程和定时器方面不是很懂，麻烦大神们帮小弟解惑。

[jklinux]

linux下创建线程用pthread_create函数就可以了, 具体用法可以参考"man pthread_create" 如要线程定时执行某个函数，那就在线程里做个死循环，调用函数后延时就可以了，不用再学定时器了。

[某鸟]

现在linux服务器版本也普遍支持c++11了，可以用c++ thread，用起来不要太方便～ 写法基本和lnux关系不大了，具体查c++文档。

[zhxianbin]

man pthread_create
PTHREAD_CREATE(3)                                 Linux Programmer's Manual                                PTHREAD_CREATE(3)

NAME
       pthread_create - create a new thread

SYNOPSIS
       #include <pthread.h>

       int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                          void *(*start_routine) (void *), void *arg);

       Compile and link with -pthread.

DESCRIPTION
       The  pthread_create() function starts a new thread in the calling process.  The new thread starts execution by invok‐
       ing start_routine(); arg is passed as the sole argument of start_routine().

       The new thread terminates in one of the following ways:

       * It calls pthread_exit(3), specifying an exit status value that is available to another thread in the  same  process
         that calls pthread_join(3).

       * It  returns  from  start_routine().   This  is equivalent to calling pthread_exit(3) with the value supplied in the
         return statement.

       * It is canceled (see pthread_cancel(3)).

       * Any of the threads in the process calls exit(3), or the main thread performs a return from main().  This causes the
         termination of all threads in the process.

       The  attr  argument points to a pthread_attr_t structure whose contents are used at thread creation time to determine
       attributes for the new thread; this structure is initialized using pthread_attr_init(3) and  related  functions.   If
       attr is NULL, then the thread is created with default attributes.

       Before  returning,  a successful call to pthread_create() stores the ID of the new thread in the buffer pointed to by
       thread; this identifier is used to refer to the thread in subsequent calls to other pthreads functions.

       The new thread inherits a copy of the creating thread's signal mask (pthread_sigmask(3)).  The set of pending signals
       for  the new thread is empty (sigpending(2)).  The new thread does not inherit the creating thread's alternate signal
       stack (sigaltstack(2)).

       The new thread inherits the calling thread's floating-point environment (fenv(3)).

       The initial value of the new thread's CPU-time clock is 0 (see pthread_getcpuclockid(3)).

   Linux-specific details
       The new thread inherits copies of the calling thread's capability sets (see capabilities(7)) and  CPU  affinity  mask
       (see sched_setaffinity(2)).

RETURN VALUE
       On  success,  pthread_create() returns 0; on error, it returns an error number, and the contents of *thread are unde‐
       fined.

ERRORS
       EAGAIN Insufficient resources to create another thread, or a system-imposed  limit  on  the  number  of  threads  was
              encountered.   The  latter  case  may  occur  in two ways: the RLIMIT_NPROC soft resource limit (set via setr‐
              limit(2)), which limits the number of process for a real user ID, was reached;  or  the  kernel's  system-wide
              limit on the number of threads, /proc/sys/kernel/threads-max, was reached.

       EINVAL Invalid settings in attr.

       EPERM  No permission to set the scheduling policy and parameters specified in attr.

CONFORMING TO
       POSIX.1-2001.

NOTES
       See  pthread_self(3)  for further information on the thread ID returned in *thread by pthread_create().  Unless real-
       time scheduling policies are being employed, after a call to pthread_create(), it is indeterminate  which  thread—the
       caller or the new thread—will next execute.

       A  thread  may either be joinable or detached.  If a thread is joinable, then another thread can call pthread_join(3)
       to wait for the thread to terminate and fetch its exit status.  Only when  a  terminated  joinable  thread  has  been
       joined  are  the last of its resources released back to the system.  When a detached thread terminates, its resources
       are automatically released back to the system: it is not possible to join with the thread in order to obtain its exit
       status.   Making  a thread detached is useful for some types of daemon threads whose exit status the application does
       not need to care about.  By default, a new thread is created in a joinable state, unless attr was set to  create  the
       thread in a detached state (using pthread_attr_setdetachstate(3)).

       On Linux/x86-32, the default stack size for a new thread is 2 megabytes.  Under the NPTL threading implementation, if
       the RLIMIT_STACK soft resource limit at the time the program started has any value other than  "unlimited",  then  it
       determines  the  default stack size of new threads.  Using pthread_attr_setstacksize(3), the stack size attribute can
       be explicitly set in the attr argument used to create a thread, in order to  obtain  a  stack  size  other  than  the
       default.

BUGS
       In the obsolete LinuxThreads implementation, each of the threads in a process has a different process ID.  This is in
       violation of the POSIX threads specification, and is the source of many other nonconformances to  the  standard;  see
       pthreads(7).

[zhxianbin]

EXAMPLE
       The  program  below  demonstrates the use of pthread_create(), as well as a number of other functions in the pthreads
       API.

       In the following run, on a system providing the NPTL threading implementation, the stack size defaults to  the  value
       given by the "stack size" resource limit:

           $ ulimit -s
           8192            # The stack size limit is 8 MB (0x800000 bytes)
           $ ./a.out hola salut servus
           Thread 1: top of stack near 0xb7dd03b8; argv_string=hola
           Thread 2: top of stack near 0xb75cf3b8; argv_string=salut
           Thread 3: top of stack near 0xb6dce3b8; argv_string=servus
           Joined with thread 1; returned value was HOLA
           Joined with thread 2; returned value was SALUT
           Joined with thread 3; returned value was SERVUS

       In the next run, the program explicitly sets a stack size of 1MB (using pthread_attr_setstacksize(3)) for the created
       threads:

           $ ./a.out -s 0x100000 hola salut servus
           Thread 1: top of stack near 0xb7d723b8; argv_string=hola
           Thread 2: top of stack near 0xb7c713b8; argv_string=salut
           Thread 3: top of stack near 0xb7b703b8; argv_string=servus
           Joined with thread 1; returned value was HOLA
           Joined with thread 2; returned value was SALUT
           Joined with thread 3; returned value was SERVUS

   Program source

       #include <pthread.h>
       #include <string.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <errno.h>
       #include <ctype.h>

       #define handle_error_en(en, msg) \
               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

       #define handle_error(msg) \
               do { perror(msg); exit(EXIT_FAILURE); } while (0)

       struct thread_info {    /* Used as argument to thread_start() */
           pthread_t thread_id;        /* ID returned by pthread_create() */
           int       thread_num;       /* Application-defined thread # */
           char     *argv_string;      /* From command-line argument */
       };

       /* Thread start function: display address near top of our stack,
          and return upper-cased copy of argv_string */

       static void *
       thread_start(void *arg)
       {
           struct thread_info *tinfo = arg;
           char *uargv, *p;

           printf("Thread %d: top of stack near %p; argv_string=%s\n",
                   tinfo->thread_num, &p, tinfo->argv_string);

           uargv = strdup(tinfo->argv_string);
           if (uargv == NULL)
               handle_error("strdup");

           for (p = uargv; *p != '\0'; p++)
               *p = toupper(*p);

           return uargv;
       }

       int
       main(int argc, char *argv[])
       {
           int s, tnum, opt, num_threads;
           struct thread_info *tinfo;
           pthread_attr_t attr;
           int stack_size;
           void *res;

           /* The "-s" option specifies a stack size for our threads */

           stack_size = -1;
           while ((opt = getopt(argc, argv, "s:")) != -1) {
               switch (opt) {
               case 's':
                   stack_size = strtoul(optarg, NULL, 0);
                   break;

               default:
                   fprintf(stderr, "Usage: %s [-s stack-size] arg...\n",
                           argv[0]);
                   exit(EXIT_FAILURE);
               }
           }

           num_threads = argc - optind;

           /* Initialize thread creation attributes */

           s = pthread_attr_init(&attr);
           if (s != 0)
               handle_error_en(s, "pthread_attr_init");

           if (stack_size > 0) {
               s = pthread_attr_setstacksize(&attr, stack_size);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_setstacksize");
           }

           /* Allocate memory for pthread_create() arguments */

           tinfo = calloc(num_threads, sizeof(struct thread_info));
           if (tinfo == NULL)
               handle_error("calloc");

           /* Create one thread for each command-line argument */

           for (tnum = 0; tnum < num_threads; tnum++) {
               tinfo[tnum].thread_num = tnum + 1;
               tinfo[tnum].argv_string = argv[optind + tnum];

               /* The pthread_create() call stores the thread ID into
                  corresponding element of tinfo[] */

               s = pthread_create(&tinfo[tnum].thread_id, &attr,
                                  &thread_start, &tinfo[tnum]);
               if (s != 0)
                   handle_error_en(s, "pthread_create");
           }

           /* Destroy the thread attributes object, since it is no
              longer needed */

           s = pthread_attr_destroy(&attr);
           if (s != 0)
               handle_error_en(s, "pthread_attr_destroy");

           /* Now join with each thread, and display its returned value */

           for (tnum = 0; tnum < num_threads; tnum++) {
               s = pthread_join(tinfo[tnum].thread_id, &res);
               if (s != 0)
                   handle_error_en(s, "pthread_join");

               printf("Joined with thread %d; returned value was %s\n",
                       tinfo[tnum].thread_num, (char *) res);
               free(res);      /* Free memory allocated by thread */
           }

           free(tinfo);
           exit(EXIT_SUCCESS);
       }

SEE ALSO
       getrlimit(2), pthread_attr_init(3), pthread_cancel(3), pthread_detach(3), pthread_equal(3), pthread_exit(3),
       pthread_getattr_np(3), pthread_join(3), pthread_self(3), pthreads(7)

COLOPHON
       This page is part of release 3.54 of the Linux man-pages project.  A description of the project, and information
       about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

Linux                                                    2012-08-03                                        PTHREAD_CREATE(3)