Programing python 4th page 228
1 """ 2 IPC 3 http://www.cnblogs.com/BoyXiao/archive/2011/01/01/1923828.html 4 """ 5 import os,time 6 import threading 7 8 def child(pipeout): 9 zzz = 0 10 while True: 11 time.sleep(zzz) # make parent wait 12 msg=('spam %03d ' % zzz).encode() # pipes are binary bytes 13 os.write(pipeout,msg) # send to parent 14 zzz = (zzz+1)%5 15 16 def parent(pipein): 17 while True: 18 line = os.read(pipein,32) # blocks until data sent 19 print('parent %d got [%s] at [%s]'%(os.getpid(),line,time.ctime())) 20 21 pipein,pipeout = os.pipe() 22 threading.Thread(target = child,args=(pipeout,)).start() 23 parent(pipein)
2.Bidirectional IPC
1 """ 2 location: programing python 4td page 229 3 spawn a child process/program,connect my stdin/stdput to child process's stdout/stdin 4 my reads and writes map to output and input streams of the spawn program;much like typing 5 together streams with subprocess module 6 """ 7 import os,sys 8 def spawn(prog,*args): 9 stdinFd = sys.stdin.fileno() #pass progname,cmdline args 10 stdoutFd =sys.stdin.fileno() # get desciptors for streams,normally stdin =0,stdout =1 11 12 parentStdin,childStdout = os.pipe() # make two IPC pipe changels 13 childStdin,parentStdout = os.pipe() # pipe returns(inputfd,outputfd) 14 pid = os.fork() #make a copy of this process 15 if pid: 16 os.close(childStdout) # in parent process after fork 17 os.close(childStdin) # close child ends in parent 18 os.dump2(parentStdin,stdinFd) # my sys.stdin copy = pipe1[0] 19 os.dump2(parentStdout,stdoutFd) # my sys.stdout copy = pipe2[1] 20 else: 21 os.close(parentStdin) # in child process afte fork: 22 os.close(parentStdout) # close parent ends in child 23 os.dump2(childStdin,stdinFd) # my sys.stdin copy = pipe2[0] 24 os.dump2(childStdout,stdoutFd) # my sysout copu = pipe1[1] 25 args = (prog,)+args 26 os.execvo(prog,args) # new program in this process 27 assert False,'execvp failed' # os.exec call never returns here 28 29 if __name__=='__main__': 30 mypid = os.getpid() 31 spawn('python','pipes-testchild.py','spawm') # fork child program 32 33 print('hello 1 from parent',mypid) # to child's stdin 34 35 sys.stdout.flush() # subvert stdio buffering 36 reply = input() # from child's stdout 37 sys.stderr.write('parent got: "%s" ' % reply) # stderr not tied to pipe 38 39 print('hello 2 from parent',mypid) 40 sys.stdout.flush() 41 reply = sys.stdin.readline() 42 sys.stderr.write('parent got:"%s" ' % reply[:-1]) 43
3.Named Pipes（Fifos）pages 234
Create a long-lived pipe that exists as a real named file in the filesystem. such files are called named pipes(or sometime,fifos).
虽然其是任意程序之外的，但是和计算机中真实文件有关，不依赖被其他任务所共享的内存。因此可以用于线程，进程和独立程序的IPC机制。一旦命名管道文件创建，客户端可以通过名字打开并使用正常的文件操作进行读写。其是单向流。典型的操作是，服务器程序从fifos读数据，客户端程序写数据。另外，2个fifos集可以用于实现双向通信，和匿名通信所做的一样。fifos不支持远程网络连接。
1 """ 2 name pipes;os.mkfifo is not available on windown 3 thare is no reason to fork here ,since fifo file ipes 4 are external to proceses--shared fds in parent/child processes 5 are irrelevent; 6 """ 7 import os,time,sys 8 fifoname ='/tmp/pipefifo' 9 def child(): 10 pipeout = os.open(filename,os.O_WRONLY) # open fifo pipe as fd 11 zzz = 0 12 while True: 13 time.sleep(zzz) 14 msg =('spam %03d ' %zzz).encode() 15 os.write(pipeout,msg) 16 zzz =(zzz+1)%5 17 def parent(): 18 pipein = open(fifoname,'r') # open file as text file object 19 while True: 20 line = pipein.readline()[:-1] #block until data sent 21 print('parent %d got "%s" at %s' % (os.getpid(),line,time.ctime())) 22 23 if __name__ =='__main__': 24 if not os.path.exits(filename): 25 os.mkfifo(fifename) #create a named pipe file 26 if len(sys.argv) == 1: 27 parent() # run as parent if no args 28 else: 29 child() # else run as child process