每个子进程的终端分区打印

Question

假设我们有多个子进程，如下所示，它们将一些结果实时打印到 sys.stdout 或 sys.stderr。

proc1 = subprocess.Popen(['cmd1'],
                         env=venv1,
                         stdout=sys.stdout,
                         stderr=sys.stderr, 
                         )

proc2 = subprocess.Popen(['cmd2'],
                         env=venv2,
                         stdout=sys.stdout,
                         stderr=sys.stderr, 
                         )

但是，在终端执行这个脚本后，在查看正在打印的内容时，很难区分哪个打印来自第一个进程，哪个来自第二个进程。

是否有解决方案可以分别查看每个进程的标准输出，例如终端屏幕是否可以分区并且每个分区都会显示每个进程的打印结果？

Answer 1

我已经为你写了一个 curses 应用程序，它可以满足你的要求：将终端窗口分成多个分区，然后观察不同分区中的不同输出流。

函数watch_fd_in_panes 将获取一个列表列表，其中子列表指定要在每个分区内监视哪些文件描述符。

您的示例调用代码如下所示：

import subprocess
from watcher import watch_fds_in_panes

proc1 = subprocess.Popen('for i in `seq 30`; do date; sleep 1 ; done',
                         shell=True,
                         stdout=subprocess.PIPE,
                         stderr=subprocess.PIPE,
                         )

# this process also writes something on stderr
proc2 = subprocess.Popen('ls -l /asdf; for i in `seq 20`; do echo $i; sleep 0.5; done',
                         shell=True,
                         stdout=subprocess.PIPE,
                         stderr=subprocess.PIPE,
                         )

proc3 = subprocess.Popen(['echo', 'hello'],
                         stdout=subprocess.PIPE,
                         stderr=subprocess.PIPE,
                         )

try:
    watch_fds_in_panes([[proc1.stdout.fileno(), proc1.stderr.fileno()],
                        [proc2.stdout.fileno(), proc2.stderr.fileno()],
                        [proc3.stdout.fileno(), proc3.stderr.fileno()]],
                       sleep_at_end=3.)
except KeyboardInterrupt:
    print("interrupted")
    proc1.kill()
    proc2.kill()
    proc3.kill()

要运行它，您需要以下两个文件：

panes.py

import curses

class Panes:
    """
    curses-based app that divides the screen into a number of scrollable
    panes and lets the caller write text into them
    """

    def start(self, num_panes):
        "set up the panes and initialise the app"

        # curses init
        self.num = num_panes
        self.stdscr = curses.initscr()
        curses.noecho()
        curses.cbreak()

        # split the screen into number of panes stacked vertically,
        # drawing some horizontal separator lines
        scr_height, scr_width = self.stdscr.getmaxyx()
        div_ys = [scr_height * i // self.num for i in range(1, self.num)]
        for y in div_ys:
            self.stdscr.addstr(y, 0, '-' * scr_width)
        self.stdscr.refresh()

        # 'boundaries' contains y coords of separator lines including notional
        # separator lines above and below everything, and then the panes
        # occupy the spaces between these
        boundaries = [-1] + div_ys + [scr_height]
        self.panes = []
        for i in range(self.num):
            top = boundaries[i] + 1
            bottom = boundaries[i + 1] - 1
            height = bottom - top + 1
            width = scr_width
            # create a scrollable pad for this pane, of height at least
            # 'height' (could be more to retain some scrollback history)
            pad = curses.newpad(height, width)
            pad.scrollok(True)
            self.panes.append({'pad': pad,
                               'coords': [top, 0, bottom, width],
                               'height': height})

    def write(self, pane_num, text):
        "write text to the specified pane number (from 0 to num_panes-1)"

        pane = self.panes[pane_num]
        pad = pane['pad']
        y, x = pad.getyx()
        pad.addstr(y, x, text)
        y, x = pad.getyx()
        view_top = max(y - pane['height'], 0)
        pad.refresh(view_top, 0, *pane['coords'])

    def end(self):
        "restore the original terminal behaviour"

        curses.nocbreak()
        self.stdscr.keypad(0)
        curses.echo()
        curses.endwin()

和watcher.py

import os
import select
import time

from panes import Panes


def watch_fds_in_panes(fds_by_pane, sleep_at_end=0):
    """
    Use panes to watch output from a number of fds that are writing data.

    fds_by_pane contains a list of lists of fds to watch in each pane.
    """
    panes = Panes()
    npane = len(fds_by_pane)
    panes.start(npane)
    pane_num_for_fd = {}
    active_fds = []
    data_tmpl = {}
    for pane_num, pane_fds in enumerate(fds_by_pane):
        for fd in pane_fds:
            active_fds.append(fd)
            pane_num_for_fd[fd] = pane_num
            data_tmpl[fd] = bytes()
    try:
        while active_fds:
            all_data = data_tmpl.copy()
            timeout = None
            while True:
                fds_read, _, _ = select.select(active_fds, [], [], timeout)
                timeout = 0
                if fds_read:
                    for fd in fds_read:
                        data = os.read(fd, 1)
                        if data:
                            all_data[fd] += data
                        else:
                            active_fds.remove(fd)  # saw EOF
                else:
                    # no more data ready to read
                    break
            for fd, data in all_data.items():
                if data:
                    strng = data.decode('utf-8')
                    panes.write(pane_num_for_fd[fd], strng)
    except KeyboardInterrupt:
        panes.end()
        raise

    time.sleep(sleep_at_end)
    panes.end()

最后，这是上面代码的截图：

在本例中，我们同时监控相关分区中每个进程的 stdout 和 stderr。在屏幕截图中，proc2 在循环开始之前写入 stderr 的行（关于/asdf）出现在 proc2 在循环的第一次迭代期间写入 stdout 的第一行之后（即1，此后滚动到分区顶部），但这是无法控制的，因为它们被写入不同的管道。