当我的代码放在`/usr/bin/` 中时，为什么进程会这么快停止？

Question

我正在尝试创建一个命令，该命令对给定进程的内存使用和 CPU 时间使用施加硬限制，如果它超过这些限制，则将其杀死。该命令还必须在进程结束时输出内存使用情况和 CPU 时间使用情况（无论进程是否被杀死）。

这是我的代码。

# Get arguments
MaxMemory="$1"
MaxTime="$2"
Command="$3"
for (( i=4 ; i<="$#"; i++)); do
    Command="${Command} ${!i}"
done

echo -e "MaxMemory = ${MaxMemory}\nMaxTime = ${MaxTime}\nCommand = ${Command}"


#### run the given command in the background
${command} &


#### Get pid
pid=$!
echo "pid = ${pid}"


#### Monitor resources
MemoryPeak=0
timeBefore=$(date +"%s")
while true;do
    # Get memory
    mem=$(ps -o rss,pid | grep ${pid} | awk '{print $1}')

    # Break if the process has stopped running
    if [[ ${mem} == "" ]]; then
        echo "process has stopped"
        break
    fi

    # Set the MemoryPeak of memory
    if (( MemoryPeak < mem )); then
        MemoryPeak=mem
    fi

    # If it consumed too much memory, then kill
    if (( MemoryPeak > MaxMemory ));then
        echo "process consumed too much memory"
        kill ${pid}
        break
    fi

    # If it consumed too much CPU time, then kill
    timeAfter=$(date +"%s")
    timeUsage=$((timeAfter - timeBefore))
    if (( timeUsage > MaxTime ));then
        echo "process consumed too much time"
        kill ${pid}
        break
    fi

    # sleep
    sleep 0.1
done

timeAfter=$(date +"%s")
timeUsage=$((timeAfter - timeBefore))

echo "MEM ${MemoryPeak} TIME ${timeUsage}"

这里显示的代码exaclty放在/usr/bin/memAndTime的文件中，我用chmod授予它访问权限。当我在终端中设置参数并直接在终端上复制粘贴其余代码时，它似乎工作正常，但不知何故当我这样做时

memAndTime 50000 5000 sleep 3s

该过程几乎在输出的同时停止

MaxMemory = 50000
MaxTime = 5000
Command = sleep 3s
pid = 31430
process has stopped
MEM 0 TIME 0

出了什么问题？

Answer 1

这是ShellCheck 的输出：

Line 13:
${command} &
^-- SC2154: command is referenced but not assigned (for output from commands, use "$(command ...)" ).

您定义的变量使用大写字母 C。

但是，您确实应该改用ulimit