在循环 bash 中等待
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Wait inside loop bash
提问by Preston Alexander
I have created a loop to read through a .txtand execute another shell using each line as input.
我创建了一个循环来读取 a.txt并使用每一行作为输入执行另一个 shell。
PROBLEM:I need the loop to execute the first two lines from the txt in parallel, wait for them to finish, then execute the next two lines in parallel.
问题：我需要循环并行执行 txt 中的前两行，等待它们完成，然后并行执行接下来的两行。
ATTEMPT AT SOLUTION:I thought of adding in a wait command, just not sure how to structure so it waits for every two lines, as opposed to each churn of the loop.
尝试解决方案：我想添加一个等待命令，只是不确定如何构建它，以便每两行等待一次，而不是循环的每次搅动。
My current loop:
我当前的循环：
cat input.txt | while read line; do
export step=${line//\"/}
export step=ExecuteModel_${step//,/_}
export pov=$line
$owsdirectory"/hpm_ws_client.sh" processCalcScriptOptions "$appName" "$pov" "$layers" "$stages" "" "$stages" "$stages" FALSE > "$appLogFolder""/"$step"_ProcessID.log"
/app/dev2/batch/hpcm/shellexe/rate_tool2/model_automation/check_process_status.sh "$appLogFolder" "$step" > "$appLogFolder""/""$step""_Monitor.log"
Input txt:
输入txt：
SEQ010,FY15
SEQ010,FY16
SEQ020,FY15
SEQ020,FY16
SEQ030,FY15
SEQ030,FY16
SEQ030,FY15
SEQ030,FY16
SEQ040,FY15
SEQ040,FY16
SEQ050,FY15
SEQ050,FY16
回答by that other guy
Normally you'd use sem, xargsor parallelto parallelize a loop, but all these tools optimize throughput by always having 2 (or N) jobs running in parallel, and starting new ones as old ones finish.
通常您会使用sem,xargs或parallel来并行化循环，但所有这些工具都通过始终并行运行 2 个（或 N 个）作业并在旧作业完成时启动新作业来优化吞吐量。
To instead run pairs of jobs and wait for both to finish before considering starting more, you can just run them in the background and keep a counter to waitevery N iterations:
要运行成对的作业并在考虑启动更多作业之前等待它们完成，您可以在后台运行它们并保持wait每 N 次迭代的计数器：
printf "%s\n" {1..10} | while IFS= read -r line
do
echo "Starting command"
sleep 2 &
if (( ++i % 2 == 0 ))
then
echo "Waiting..."
wait
fi
done
Output:
输出：
Starting command
Starting command
Waiting...
Starting command
Starting command
Waiting...
