2010-05-03

并行运行多进程的Bash脚本 | A srcipt for running processes in parallel in Bash

原文:http://pebblesinthesand.wordpress.com/2008/05/22/a-srcipt-for-running-processes-in-parallel-in-bash/

技巧是控制了最大并发数目,当前并发数过大时,等待有进程退出才开始下一个。

我现在正在写的脚本里正需要这个,借鉴过来


#!/bin/bash
NUM=0
QUEUE=""
MAX_NPROC=2 # default
REPLACE_CMD=0 # no replacement by default
USAGE="A simple wrapper for running processes in parallel.
Usage: `basename $0` [-h] [-r] [-j nb_jobs] command arg_list
-h Shows this help
-r Replace asterix * in the command string with argument
-j nb_jobs Set number of simultanious jobs [2]
Examples:
`basename $0` somecommand arg1 arg2 arg3
`basename $0` -j 3 \"somecommand -r -p\" arg1 arg2 arg3
`basename $0` -j 6 -r \"convert -scale 50% * small/small_*\" *.jpg"

function queue {
QUEUE="$QUEUE $1"

NUM=$(($NUM+1))
}

function regeneratequeue {
OLDREQUEUE=$QUEUE
QUEUE=""
NUM=0
for PID in $OLDREQUEUE
do
if [ -d /proc/$PID ] ; then
QUEUE="$QUEUE $PID"
NUM=$(($NUM+1))
fi
done
}

function checkqueue {
OLDCHQUEUE=$QUEUE
for PID in $OLDCHQUEUE
do
if [ ! -d /proc/$PID ] ; then
regeneratequeue # at least one PID has finished
break
fi
done
}

# parse command line
if [ $# -eq 0 ]; then # must be at least one arg
echo "$USAGE" >&2
exit 1
fi

while getopts j:rh OPT; do # "j:" waits for an argument "h" doesnt
case $OPT in
h) echo "$USAGE"

exit 0 ;;
j) MAX_NPROC=$OPTARG ;;
r) REPLACE_CMD=1 ;;
\?) # getopts issues an error message
echo "$USAGE" >&2
exit 1 ;;
esac
done

# Main program
echo Using $MAX_NPROC parallel threads
shift `expr $OPTIND - 1` # shift input args, ignore processed args
COMMAND=$1
shift

for INS in $* # for the rest of the arguments
do
# DEFINE COMMAND
if [ $REPLACE_CMD -eq 1 ]; then
CMD=${COMMAND//"*"/$INS}
else
CMD="$COMMAND $INS" #append args
fi
echo "Running $CMD"

$CMD &
# DEFINE COMMAND END

PID=$!
queue $PID

while [ $NUM -ge $MAX_NPROC ]; do
checkqueue
sleep 0.4
done
done
wait # wait for all processes to finish before exit






Original posted at: http://pebblesinthesand.wordpress.com/2008/05/22/a-srcipt-for-running-processes-in-parallel-in-bash/

This script will run multiple process in background concurrently, while the maximum number of running processed is under control. When there are already too many running processes, a new one will wait until one process finished.

I just need this trick in my project, so I copied it here.

(See codes above)
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