[英]Modify a variable in a running Bash script
我有一個處理幾年數據的bash腳本,因此腳本可能需要一周的時間才能完成。 為了加快這個過程,我使用多線程,並行運行多個實例(每個實例= 1天的數據)。 每個實例占用1個CPU,因此我可以運行與可用CPU一樣多的實例。 當我在一個功能強大的服務器上運行該進程時,我正在與其他人共享,有時我可能會有更多或更少的CPU可用。 我目前的腳本是:
#!/bin/bash
function waitpid {
#Gather the gLABs PID background processes (Maximum processes in
#background as number of CPUs)
NUMPIDS=`jobs -p|awk 'END {print NR}'`
#A while is set because there seems to be a bug in bash that makes
#sometimes the "wait -n" command
#exit even if none of provided PIDs have finished. If this happens,
#the while loops forces the
#script to wait until one of the processes is truly finished
while [ ${NUMPIDS} -ge ${NUMCPUS} ]
do
#Wait for gLAB processes to finish
PIDS="`jobs -p|awk -v ORS=" " '{print}'`"
wait -n ${PIDS} >/dev/null 2>/dev/null
NUMPIDS=`jobs -p|awk 'END {print NR}'`
done
}
NUMPCUS=10
for(...) #Loop for each day
do
day=... #Set current day variable
#Command to execute, put in background
gLAB_linux -input ${day}folder/${day}.input -output ${day)outfolder/${day}.output &
#Wait for any process to finish if NUMCPUS number of processes are running in background
waitpid
done
因此,我的問題是:如果此腳本正在運行,是否有任何方法可以在不停止腳本的情況下將變量NUMCPUS更改為任何值(例如NUMCPUS = 23)? 如果可能的話,我更喜歡一種不涉及讀取或寫入文件的方法(如果可能的話,我喜歡將臨時文件減少到0)。 我不介意它是否是一個“hackish”過程,例如本答案中描述的方法。 實際上,我在gdb中嘗試了類似於該答案的命令,但是它沒有用,我在gdb中遇到了以下錯誤(並且還使進程崩潰):
(gdb) attach 23865
(gdb) call bind_variable("NUMCPUS",11,0)
'bind_variable' has unknown return type; cast the call to its declared return type
(gdb) call (int)bind_variable("NUMCPUS",11,0)
Program received signal SIGSEGV, Segmentation fault
EDIT1:對腳本的一些評論:
wait -n
內部休眠。 編輯2:在@Kamil回答之后,我添加了我的建議,從文件中讀取CPU的數量
function waitpid {
#Look if there is a file with new number of CPUs
if [ -s "/tmp/numCPUs_$$.txt" ]
then
TMPVAR=$(awk '$1>0 {print "%d",$1} {exit}' "/tmp/numCPUs_$$.txt")
if [ -n "${TMPVAR}" ]
then
NUMCPUS=${TMPVAR}
echo "NUMCPUS=${TMPVAR}"
fi
rm -f "/tmp/numCPUs_$$.txt"
fi
#Gather the gLABs PID background processes (Maximum processes in
#background as number of CPUs)
NUMPIDS=`jobs -p|awk 'END {print NR}'`
#A while is set because there seems to be a bug in bash that makes
#sometimes the "wait -n" command
#exit even if none of provided PIDs have finished. If this happens,
#the while loops forces the
#script to wait until one of the processes is truly finished
while [ ${NUMPIDS} -ge ${NUMCPUS} ]
do
#Wait for gLAB processes to finish
PIDS="`jobs -p|awk -v ORS=" " '{print}'`"
wait -n ${PIDS} >/dev/null 2>/dev/null
NUMPIDS=`jobs -p|awk 'END {print NR}'`
done
}
最好的方法是修改bash腳本,以便它知道你改變了值。 從gdb會話中修改環境變量 - 這只是侵入性的,並且主要是丟棄其他開發人員的工作。
下面我使用名為/tmp/signal_num_cpus
的文件。 如果該文件不存在,則腳本使用NUMCPUS值。 如果文件存在,則會讀取內容並相應地更新NUMCPUS的數量,然后打印一些numcpus已更改為文件的通知。 如果文件存在且不包含有效數字(例如,在預定義范圍或smth中),則會在文件中輸出一些錯誤消息。 另一方通知一切正常或發生了一些不好的事情
#!/bin/bash
is_not_number() {
(( $1 != $1 )) 2>/dev/null
}
# global variable to hold the number of cpus with a default value
NUMCPUS=${NUMCPUS:=5}
# this will ideally execute on each access to NUMCPUS variable
# depending on content
get_num_cpus() {
# I tell others that NUMCPUS is a global variable and i expect it here
declare -g NUMCPUS
# I will use this filename to communicate
declare -r file="/tmp/signal_num_cpus"
# If the file exists and is a fifo...
if [ -p "$file" ]; then
local tmp
# get file contents
tmp=$(<"$file")
if [ -z "$tmp" ]; then
#empty is ignored
:;
elif is_not_number "$tmp"; then
echo "Error reading a number from $file" >&2
echo "error: not a number, please give me a number!" > "$file"
else
# If it is ok, update the NUMCPUS value
NUMCPUS=$tmp
echo "ok $NUMCPUS" > "$file" # this will block until other side starts reading
fi
fi
# last but not least, let's output it
echo "$NUMCPUS"
}
# code duplication is the worst (ok, sometimes except for databases frameworks)
get_num_bg_jobs() {
jobs -p | wc -l
}
waitpid() {
while
(( $(get_num_bg_jobs) >= $(get_num_cpus) ))
do
wait -n
done
}
# rest of the script
NUMPCUS=10
for(...) #Loop for each day
do
day=... #Set current day variable
#Command to execute, put in background
gLAB_linux -input "${day}folder/${day}.input" -output "${day)outfolder/${day}.output" &
#Wait for any process to finish if NUMCPUS number of processes are running in background
waitpid
done
更改值腳本可能如下所示:
#!/bin/bash
# shared context between scripts
declare -r file="/tmp/signal_num_cpus"
mkfifo "$file"
echo 1 > "$file" # this will block until other side will start reading
IFS= read -r line < "$file"
case "$line" in
ok*)
read _ numcpus <<<"$line"
echo "the script changed the number of numcpus to $numcpus"
;;
*)
echo "the script errored with $error"
;;
esac
rm "$file"
分數:
func() { :; }
func() { :; }
使用function func { }
是從KSH采取財產以后並且被支撐為擴展。 使用func() {}
(( ... ))
進行數字比較和處理。 $( ... )
已棄用。 GNU Parallel 2018的第7.1章介紹了如何在運行https://zenodo.org/record/1146014時更改要使用的線程數
echo 50% > my_jobs
/usr/bin/time parallel -N0 --jobs my_jobs sleep 1 :::: num128 &
sleep 1
echo 0 > my_jobs
wait
所以你只需將--jobs
的參數放入my_jobs
,GNU Parallel將在每個完成的作業后讀取它。
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