如何在bash脚本中等待从该脚本派生的几个子进程完成,然后在任何子进程以code !=0结束时返回退出代码!=0?
简单的脚本:
#!/bin/bash
for i in `seq 0 9`; do
doCalculations $i &
done
wait
上面的脚本将等待所有10个子进程,但它总是给出退出状态0(参见help wait)。我如何修改这个脚本,以便它将发现衍生子进程的退出状态,并在任何子进程以code !=0结束时返回退出代码1 ?
有没有比收集子进程的pid、按顺序等待它们并求和退出状态更好的解决方案呢?
下面是我的版本,适用于多个pid,如果执行时间过长,则记录警告,如果执行时间超过给定值,则停止子进程。
[编辑]我已经在https://github.com/deajan/ofunctions上传了我的WaitForTaskCompletion的新实现,称为ExecTasks。
还有一个用于WaitForTaskCompletion的compat层
(/编辑)
function WaitForTaskCompletion {
local pids="${1}" # pids to wait for, separated by semi-colon
local soft_max_time="${2}" # If execution takes longer than $soft_max_time seconds, will log a warning, unless $soft_max_time equals 0.
local hard_max_time="${3}" # If execution takes longer than $hard_max_time seconds, will stop execution, unless $hard_max_time equals 0.
local caller_name="${4}" # Who called this function
local exit_on_error="${5:-false}" # Should the function exit program on subprocess errors
Logger "${FUNCNAME[0]} called by [$caller_name]."
local soft_alert=0 # Does a soft alert need to be triggered, if yes, send an alert once
local log_ttime=0 # local time instance for comparaison
local seconds_begin=$SECONDS # Seconds since the beginning of the script
local exec_time=0 # Seconds since the beginning of this function
local retval=0 # return value of monitored pid process
local errorcount=0 # Number of pids that finished with errors
local pidCount # number of given pids
IFS=';' read -a pidsArray <<< "$pids"
pidCount=${#pidsArray[@]}
while [ ${#pidsArray[@]} -gt 0 ]; do
newPidsArray=()
for pid in "${pidsArray[@]}"; do
if kill -0 $pid > /dev/null 2>&1; then
newPidsArray+=($pid)
else
wait $pid
result=$?
if [ $result -ne 0 ]; then
errorcount=$((errorcount+1))
Logger "${FUNCNAME[0]} called by [$caller_name] finished monitoring [$pid] with exitcode [$result]."
fi
fi
done
## Log a standby message every hour
exec_time=$(($SECONDS - $seconds_begin))
if [ $((($exec_time + 1) % 3600)) -eq 0 ]; then
if [ $log_ttime -ne $exec_time ]; then
log_ttime=$exec_time
Logger "Current tasks still running with pids [${pidsArray[@]}]."
fi
fi
if [ $exec_time -gt $soft_max_time ]; then
if [ $soft_alert -eq 0 ] && [ $soft_max_time -ne 0 ]; then
Logger "Max soft execution time exceeded for task [$caller_name] with pids [${pidsArray[@]}]."
soft_alert=1
SendAlert
fi
if [ $exec_time -gt $hard_max_time ] && [ $hard_max_time -ne 0 ]; then
Logger "Max hard execution time exceeded for task [$caller_name] with pids [${pidsArray[@]}]. Stopping task execution."
kill -SIGTERM $pid
if [ $? == 0 ]; then
Logger "Task stopped successfully"
else
errrorcount=$((errorcount+1))
fi
fi
fi
pidsArray=("${newPidsArray[@]}")
sleep 1
done
Logger "${FUNCNAME[0]} ended for [$caller_name] using [$pidCount] subprocesses with [$errorcount] errors."
if [ $exit_on_error == true ] && [ $errorcount -gt 0 ]; then
Logger "Stopping execution."
exit 1337
else
return $errorcount
fi
}
# Just a plain stupid logging function to be replaced by yours
function Logger {
local value="${1}"
echo $value
}
例如,等待所有三个进程完成,如果执行时间超过5秒,则记录警告,如果执行时间超过120秒,则停止所有进程。不要在失败时退出程序。
function something {
sleep 10 &
pids="$!"
sleep 12 &
pids="$pids;$!"
sleep 9 &
pids="$pids;$!"
WaitForTaskCompletion $pids 5 120 ${FUNCNAME[0]} false
}
# Launch the function
someting
为了将此并行化…
for i in $(whatever_list) ; do
do_something $i
done
翻译成这样…
for i in $(whatever_list) ; do echo $i ; done | ## execute in parallel...
(
export -f do_something ## export functions (if needed)
export PATH ## export any variables that are required
xargs -I{} --max-procs 0 bash -c ' ## process in batches...
{
echo "processing {}" ## optional
do_something {}
}'
)
If an error occurs in one process, it won't interrupt the other processes, but it will result in a non-zero exit code from the sequence as a whole.
Exporting functions and variables may or may not be necessary, in any particular case.
You can set --max-procs based on how much parallelism you want (0 means "all at once").
GNU Parallel offers some additional features when used in place of xargs -- but it isn't always installed by default.
The for loop isn't strictly necessary in this example since echo $i is basically just regenerating the output of $(whatever_list). I just think the use of the for keyword makes it a little easier to see what is going on.
Bash string handling can be confusing -- I have found that using single quotes works best for wrapping non-trivial scripts.
You can easily interrupt the entire operation (using ^C or similar), unlike the the more direct approach to Bash parallelism.
下面是一个简化的工作示例……
for i in {0..5} ; do echo $i ; done |xargs -I{} --max-procs 2 bash -c '
{
echo sleep {}
sleep 2s
}'