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[TOC]
| 代码示例支持 |
|---|
| 平台: Centos 6.3 |
| Python: 2.7.14 |
| Github: https://github.com/baidu/CUP |
欢迎关注公众号进行技术互动和讨论:
今天的坑不仅包括裸用os.system还包括裸用相关的家族:
这些坑是新同学非常容易踩，而且 code review 过程中容易漏掉:
[1] 长期运行 Service 中裸用以函数家族
[2] 自动化测试中裸用以上函数家族而不加以保护
提供一个作者的代码参考: https://github.com/baidu/CUP/blob/master/cup/shell/oper.py
from cup import shell
shellexec = shell.ShellExec()
# timeout=None will block the execution until it finishes
shellexec.run('/bin/ls', timeout=None)
# timeout>=0 will open non-blocking mode
# The process will be killed if the cmd timeouts
shellexec.run(cmd='/bin/ls', timeout=100)见ShellExec类的run函数
建议看下第二章节关于进程和子进程继承类信息，script使用上述家族进行执行时，采用了启动一个子进程的方式
Shell执行是个非常常见的操作，所以很多同学特别是新同学，在使用过程中经常不注意而随意使用。 裸用一时爽，进程死亡火葬场
参考资料来源:
man fork )
fork() creates a new process by duplicating the calling process. The new process, referred to as the child, is an exact duplicate of the calling process, referred to as the parent, except for the follow-
ing points:
* The child has its own unique process ID, and this PID does not match the ID of any existing process group (setpgid(2)).
* The child's parent process ID is the same as the parent's process ID.
* The child does not inherit its parent's memory locks (mlock(2), mlockall(2)).
* Process resource utilizations (getrusage(2)) and CPU time counters (times(2)) are reset to zero in the child.
* The child's set of pending signals is initially empty (sigpending(2)).
* The child does not inherit semaphore adjustments from its parent (semop(2)).
* The child does not inherit record locks from its parent (fcntl(2)).
* The child does not inherit timers from its parent (setitimer(2), alarm(2), timer_create(2)).
* The child does not inherit outstanding asynchronous I/O operations from its parent (aio_read(3), aio_write(3)), nor does it inherit any asynchronous I/O contexts from its parent (seeio_setup(2)).
The process attributes in the preceding list are all specified in POSIX.1-2001. The parent and child also differ with respect to the following Linux-specific process attributes:
* The child does not inherit directory change notifications (dnotify) from its parent (see the description of F_NOTIFY in fcntl(2)).
* The prctl(2) PR_SET_PDEATHSIG setting is reset so that the child does not receive a signal when its parent terminates.
* Memory mappings that have been marked with the madvise(2) MADV_DONTFORK flag are not inherited across a fork().
* The termination signal of the child is always SIGCHLD (see clone(2)).
在说继承、拷贝父进程的
此外
在 Linux 系统中， 一般系统会自动替程序选择端口连接到用户指定的目的端口， 而这个端口范围是提前设定好的， 比如作者的 centos：
$ cat /proc/sys/net/ipv4/ip_local_port_range
10000 60000欢迎关注公众号进行技术互动和讨论:
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