如何使用bash查找给定进程的顶级父PID?

Bash绝对可以做递归。

您可以从stat文件中检索第四个字段,而无需使用外部 cut 通过这样做:

stat=($(</proc/$$/stat))    # create an array
ppid=${stat[3]}             # get the fourth field

如果命令名中可能有空格,则可以从数组末尾开始计数(假设 number of fields 是稳定的)。如果命令名中没有空格,也可以这样做。

ppid=${stat[-49]}           # gets the same field but counts from the end

下面是另一种可以避免这些问题的技术(但如果命令名包含换行符,则可能会失败):

mapfile -t stat < /proc/$$/status
ppid=${stat[5]##*$'\t'}

该文件中的第五个字段如下所示:

PPid:    1234

大括号展开将所有内容剥离到tab字符,只留下数字部分。

如果没有更好的解决方案,下面是一个简单的(递归)脚本,用于获取给定的任何进程号的顶级父PID(如果忽略PID参数,则获取当前shell):

#!/bin/bash
# Look up the top-level parent Process ID (PID) of the given PID, or the current
# process if unspecified.

function top_level_parent_pid {
    # Look up the parent of the given PID.
    pid=${1:-$$}
    stat=($(</proc/${pid}/stat))
    ppid=${stat[3]}

    # /sbin/init always has a PID of 1, so if you reach that, the current PID is
    # the top-level parent. Otherwise, keep looking.
    if [[ ${ppid} -eq 1 ]] ; then
        echo ${pid}
    else
        top_level_parent_pid ${ppid}
    fi
}

source 这个脚本和调用 top_level_parent_pid 带或不带PID参数(视情况而定)。

感谢@Dennis Williamson对如何简洁高效地编写这个脚本提出了许多建议。

另一个解决方案(来自 here

ps -p $$ -o ppid=

迭代版本:

# ppid -- Show parent PID
# $1 - The process whose parent you want to show, default to $$
function ppid() {
    local stat=($(</proc/${1:-$$}/stat))
    echo ${stat[3]}
}

# apid -- Show all ancestor PID
# $1 - The process whose ancestors you want to show, default to $$
# $2 - Stop when you reach this ancestor PID, default to 1
function apid() {
    local ppid=$(ppid ${1:$$})
    while [ 0 -lt $ppid -a ${2:-1} -ne $ppid ]; do
        echo $ppid
        ppid=$(ppid $ppid)
    done
}

作为两个独立的函数,因为有时只需要父PID,有时需要整个树。

#!/bin/bash
# Look up the top-level parent Process ID (PID) of the given PID, or the current
# process if unspecified.

function top_level_parent_pid {
    # Look up the parent of the given PID.
    pid=${1:-$$}
    ppid="$(awk '/^PPid:/ { print $2 }' < /proc/"$pid"/status)"
    # /sbin/init always has a PID of 1, so if you reach that, the current PID is
    # the top-level parent. Otherwise, keep looking.
    if [[ ${ppid} -eq 1 ]] ; then
        echo "${pid}"
    else
        top_level_parent_pid "${ppid}"
    fi
}

OS X版本 ,改编自@albert和@yukondude的答案:

#!/usr/bin/env bash
# Look up the top-level parent Process ID (PID) of the given PID, or the current
# process if unspecified.

# From http://stackoverflow.com/questions/3586888/how-do-i-find-the-top-level-parent-pid-of-a-given-process-using-bash
function top_level_parent_pid {
    # Look up the parent of the given PID.
    PID=${1:-$$}
    PARENT=$(ps -p $PID -o ppid=)

    # /sbin/init always has a PID of 1, so if you reach that, the current PID is
    # the top-level parent. Otherwise, keep looking.
    if [[ ${PARENT} -eq 1 ]] ; then
        echo ${PID}
    else
        top_level_parent_pid ${PARENT}
    fi
}