进程替换或 FIFO 中的命令何时开始和结束运行?

进程替换或 FIFO 中的命令何时开始和结束运行?

bash 中进程替换中的命令何时开始和完成运行?例如

  • 分别什么时候command1开始command2 >(command1) 和结束运行?

  • 分别什么时候command3开始command4 <(command3) 和结束运行?

FIFO 中的命令何时开始和结束运行?例如

  • 分别什么时候prog2开始mkfifo fifo1; prog2 < fifo1 &; prog1 > fifo1;和结束运行?
  • 分别什么时候prog3开始mkfifo fifo2; prog3 > fifo12 &; prog2 < fifo2;和结束运行?

谢谢。

答案1

实验上,在 bash 中:

$ strace -tttfe execve bash -c 'sleep 5 <(sleep 6)'
1522025733.188859 execve("/bin/bash", ["bash", "-c", "sleep 5 <(sleep 6)"], [/* 41 vars */]) = 0
strace: Process 24248 attached
[pid 24247] 1522025733.215188 execve("/bin/sleep", ["sleep", "5", "/dev/fd/63"], [/* 41 vars */]) = 0
strace: Process 24249 attached
[pid 24249] 1522025733.218331 execve("/bin/sleep", ["sleep", "6"], [/* 41 vars */]) = 0
sleep: invalid time interval ‘/dev/fd/63’
Try 'sleep --help' for more information.
[pid 24247] 1522025733.227459 +++ exited with 1 +++
[pid 24249] 1522025739.230933 +++ exited with 0 +++
1522025739.232270 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=24249, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
1522025739.233169 +++ exited with 0 +++
$ strace -tttfe execve bash -c 'sleep 5 >(sleep 6)'
1522025752.162876 execve("/bin/bash", ["bash", "-c", "sleep 5 >(sleep 6)"], [/* 41 vars */]) = 0
strace: Process 24253 attached
[pid 24252] 1522025752.188413 execve("/bin/sleep", ["sleep", "5", "/dev/fd/63"], [/* 41 vars */]) = 0
strace: Process 24254 attached
[pid 24254] 1522025752.191032 execve("/bin/sleep", ["sleep", "6"], [/* 41 vars */]) = 0
sleep: invalid time interval ‘/dev/fd/63’
Try 'sleep --help' for more information.
[pid 24252] 1522025752.197213 +++ exited with 1 +++
[pid 24254] 1522025758.197114 +++ exited with 0 +++
1522025758.197959 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=24254, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
1522025758.198820 +++ exited with 0 +++

command1并分别在和command3之后开始。command2command4

只要满足退出或被杀死的条件,他们就会退出。


makefifo fifo1; prog2 < fifo1 &; prog1 > fifo1;makefifo fifo2; prog3 > fifo12 &; prog2 < fifo2;是语法错误,至少在 bash 中是这样。即使不是,我也没有在重定向中看到任何会导致与没有重定向时不同的执行顺序的内容。

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