c - 从叶子开始逐级修剪二叉流程树

Question

我需要编写一个运行 C 程序的 bash 脚本，该程序使用 fork() 生成一个 n 深度的进程二叉树，然后从树的叶子开始逐级修剪它到根。

制作进程树的C代码非常简单。 You can see the full code here , 但 TL;DR 版本如下:

void tree(int n):
   if (n==0) exit
   rchild=fork()
   if (parent)
      lchild=fork()
      if (left child)
         tree(n-1)
   else //right child
      tree(n-1)
sleep(1000)

查看 pstree -pn PID 输出我注意到 child 的 PID 是连续的，所以我决定根据第一个实例的 PID 按数值终止进程。但也许是因为命令占用了 PID 值或其他系统进程，在脚本中运行代码会破坏 PID 的值，所以我的方法不再有效。我正在尝试通过使用 pstree 的输出直接获取 PID，但目前看来它会是一堆 sed 和 awk 调用只是为了获得一个PID 级别。

这是我目前拥有的 bash 脚本:

#!/bin/bash

if [ ! -f "./fork.run" ]
then
    >&2 echo 'Error: binary mising'
    >&2 echo 'Generate it with "gcc -o fork.run fork.c"'
    exit
fi

if [ "$1" == "" ]
then
    >&2 echo "Error: you need to indicate the depth of the tree"
    exit
fi

./fork.run $(( $1 - 1 )) &
fork=$! #store tree's PID
n=$1

echo "fork started with PID $fork"


while [ $n -gt 1 ]
do

    echo "Tree of the process $fork:"
    pstree -pn $fork

    sleep 1

    #calculation based on properties of the binary tree
    min=$(( 2 ** (n - 1) + $fork ))
    max=$(( (2 ** n) - 1 + $fork ))

    echo "starting trim: level $n"


    for i in `seq $min $max`
    do
        echo "killing $i"
        kill $i #I also tried kill -9 $i, but it's the same.
    done

    sleep 1

    echo "processes from $min to $max trimmed"

    let n--
done

pstree -pn $fork

sleep 1

echo "starting trim: level $n (final)"

kill $fork

sleep 1

echo "initial process ($fork) trimmed"

Answer 1

it seems that it will be a mess of sed and awk calls just to get one level of PIDs.

好吧，awk 并不太乱。 while 循环的以下替换使用 awk 脚本处理 pstree 输出，该脚本确定(基于每行中的位置)包含的进程所属的树级别并杀死所选级别 n 上的进程。

while [ $n -gt 1 ]
do
    echo "Tree of the process $fork:"
    pstree -p $fork
    sleep 1
    echo "starting trim: level $n"
    pstree -pl $fork |
    gawk -vn=$n '
    /^[^ ]/ { level = 1; start[1] = 1 }             # line starting with non-space has top level
    /^ /    { level = trats[match($0, "[|`]-")] }   # determine first level of line from position of |- or `-
    {   while (i = match(substr($0, start[level]), ")-[-+]-"))
        { start[level+1] = start[level]+i+1; ++level; trats[start[level]] = level } # hash level by position
        if (match(substr($0, start[n]), "^.-[^(]+.([0-9]+)", p)) { print "killing "p[1]; system("kill "p[1]) }
    }   '
    sleep 1
    echo "processes trimmed"
    let n--
done