bash 错误的数组下标
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/16120155/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Bad array subscript
提问by James
I'm relatively new to Shell and I've been trying to use arrays in Shell and it's not working well. I'm trying to write a script to suspend OpenVZ containers should they hit a certain bandwidth threshold over a period of time.
我对 Shell 比较陌生，我一直在尝试在 Shell 中使用数组，但效果不佳。我正在尝试编写一个脚本来挂起 OpenVZ 容器，如果它们在一段时间内达到某个带宽阈值。
My script:
我的脚本：
#!/bin/bash
#Thresholds are in bytes per second and count1 must > count2
LOGDIR="/var/log/outbound_ddos"
SECS=10
THRESHOLD1=65536000
COUNT1=10
THRESHOLD2=117964800
COUNT2=2
while [ 1 ]
do
for veid in $(/usr/sbin/vzlist -o veid -H)
do
# Create the log file if it doesn't already exist
if ! test -e $LOGDIR/$veid.log; then
touch $LOGDIR/$veid.log
fi
# Parse out the inbound/outbound traffic and assign them to the corresponding variables
eval $(/usr/sbin/vzctl exec $veid "grep venet0 /proc/net/dev" | \
awk -F: '{print }' | awk '{printf"CTOUT=%s\n", }')
# Print the output and a timestamp to a log file
echo $(date +%s) $CTOUT >> $LOGDIR/$veid.log
# Read last 10 entries into arrays
i=0
tail $LOGDIR/$veid.log | while read time byte
do
times[$i]=time; bytes[$i]=byte
let i++
done
# Sanity checks and calculations
for (( i=0; i<COUNT1; i++ ))
do
# Sanity check on the time
if (( times[$i] > times[$i - 1] + $SECS + 10 ))
then continue
fi
# Calculate differences
let "diff[$i] = bytes[$i+1] - bytes[$i]"
done
# Work out thresholds and suspend where necessary
# Higher threshold first
t2=0
for (( i=COUNT1-1; i>=0; i-- ))
do
if [ ! diff[$i] ]
then continue
else
if (( bytes[$i] < THRESHOLD1 * SECS + bytes[$i-1] + 1 ))
then continue
else let t2++
fi
fi
done
#Lower threshold last
t1=0
for (( i=COUNT1-1; i>=0; i-- ))
do
if [ ! diff[$i] ]
then continue
else
if (( bytes[$i] < THRESHOLD1 * SECS + bytes[$i-1] + 1 ))
then continue
else let t1++
fi
fi
done
# Suspend where necessary
if (( ($t2 >= $COUNT2) || ($t1 >= $COUNT1) ))
then vzctl stop veid
fi
done
sleep $SECS
done
And the errors:
和错误：
script.sh: line 38: times: bad array subscript
script.sh: line 54: bytes: bad array subscript
script.sh: line 67: bytes: bad array subscript
I've tried several variations of the array subscript but I can't seem to get rid of those errors.
我已经尝试了数组下标的几种变体，但我似乎无法摆脱这些错误。
回答by kojiro
So on line 38,
所以在第 38 行，
if (( times[$i] > times[$i - 1] + $SECS + 10 ))
would refer to times[-1]once during the iteration. Negative indices are only very recently part of bash arrays, so that is most likely why you are getting the error.
将times[-1]在迭代期间引用一次。负索引只是最近 bash arrays 的一部分，因此这很可能是您收到错误的原因。
Likewise with lines 54 and 67 you're hitting a negative array subscript once. Adjust your loops to avoid [0 - 1].
同样，在第 54 行和第 67 行中，您会遇到一次负数组下标。调整循环以避免[0 - 1].
