等待subshell进程完成

Question

processUsageFile()
{
    #sdate=`pin_virtual_time  | awk -F" " '{print $3}'`;

    #Get all new files to be loaded to brm staging data.
    count=`ls ${PRE_STAGING}/TWN* 2>/dev/null|grep -v reprocess|wc -l`
    if [ $count -ne 0 ];then
        # Fork subshell
        (./efx_omc_brm_rpt_process.sh -t TWN & )&
        exitOnError
    fi

    #Process Rapid Report files
    count=`ls $PRE_STAGING/RR* 2>/dev/null|grep -v  reprocess|wc -l`
    if [ $count -ne 0 ];then
        (./efx_omc_brm_rpt_process.sh -t RR &)&
        exitOnError
    fi
...
...
}
#Reprocessing. Process the reprocessed files.
#This method updates the records in the BRM staging table.
reprocessingUsageFile()
{
    #Process TWN fulfillment reprocess files
    count=`ls $PRE_STAGING/TWN*reprocess* 2>/dev/null|wc -l`
    if [ $count -ne 0 ];then
        # Fork subshell
        (./efx_omc_brm_rpt_reprocess.sh -t TWN & ) &
    fi

    #Process Rapid Report files
    count=`ls $PRE_STAGING/RR*reprocess* 2>/dev/null|wc -l`
    if [ $count -ne 0 ];then
        (./efx_omc_brm_rpt_reprocess.sh -t RR &) &
    fi
...
...
}

#Pre processing
PreProcessing

# Start processing usage files.
processUsageFile

processErrFile 

上面代码的思想是进行并行处理。所有方法都调用多个子subshells并从tty中分离。我想知道是否有办法等待前两个方法先完成执行，然后再运行最后一个方法。

等待PID在某种程度上是不准确的。还在努力..。

waitPids() {
echo "Testing $pids -- ${#pids[@]}"
    while [ ${#pids[@]} -ne 0 ]; do
            local range=$(eval echo {0..$((${#pids[@]}-1))})
            local i
            for i in $range; do
                if ! kill -0 ${pids[$i]} 2> /dev/null; then
                    echo "Done -- ${pids[$i]}"
                     unset pids[$i]
                fi
            done
            pids=("${pids[@]}") 
            sleep 1
        done
    }

Answer 1

使用等待构建

$ help wait
wait: wait [-n] [id ...]
    Wait for job completion and return exit status.

    Waits for each process identified by an ID, which may be a process ID or a
    job specification, and reports its termination status.  If ID is not
    given, waits for all currently active child processes, and the return
    status is zero.  If ID is a a job specification, waits for all processes
    in that job's pipeline.

    If the -n option is supplied, waits for the next job to terminate and
    returns its exit status.

    Exit Status:
    Returns the status of the last ID; fails if ID is invalid or an invalid
    option is given.

极简主义示例

$ wait -n; (sleep 3; false); echo $?
1

您的代码示例

后台任务立即返回。您的诀窍是将函数包装在一个子subshell中，这样您就可以等待该子subshell (而不是后台作业)完成。例如：

$ wait -n; (processUsageFile); echo $?

如果想要更复杂，就必须在变量中捕获后台任务的PID，这样就可以使用wait $pidof_process_1 $pidof_process_2这样的结构等待特定的进程。

将函数包装在子subshell中会更容易。但是，您的特定需求可能会有所不同。

Answer 2

看起来主要的问题是，你使用的是分离子外壳。

也许最简单的解决方案是使用不同的机制来分离子subshells，这样您就可以使用wait。

例如，通过nohup

 nohup ./process1 &
 nohup ./process2 &
 wait

Answer 3

可能是进程和重新进程之间的“等待”命令。

来自：http://www.tldp.org/LDP/abs/html/subshells.html

例21-3。在子subshells中运行并行进程

(cat list1 list2 list3 | sort | uniq > list123) &
(cat list4 list5 list6 | sort | uniq > list456) &
# Merges and sorts both sets of lists simultaneously.
# Running in background ensures parallel execution.
#
# Same effect as
#   cat list1 list2 list3 | sort | uniq > list123 &
#   cat list4 list5 list6 | sort | uniq > list456 &

wait   # Don't execute the next command until subshells finish.

diff list123 list456