Open vieyahn2017 opened 7 months ago
前一阵用shell写了一个从数据库中抽取数据生成.xml文件的脚本,要求是每个文件中只生成1000条数据。于是用到了while read line 作为循环。
在制作文件计数器的时候发现了一个问题,在执行的过程中文件计数器(FILENUM)总是出现返回初始值的现象,具体简化的脚本如下:
#/bin/bash
FILENUM=1
for i in (多个表)
do
#sql 语句 > .swap
COUNTER=0
cat .swap | while read line
do
#变量赋值以及写入文件的内容(不是重点,没细写)
COUNTER=$[COUNTER+1]
if [ $COUNTER -eq 1000 ]
then
#封包操作,封包的包名中附带了$FILENAME(没细写)
FILENUM=$[FILENUM+1]
fi
done
#封包操作,封包的包名中附带了$FILENAME,因为不能保证是1000条整数,所以read line跳出后还是需要执行这个操作。
FILENUM=$[FILENUM+1]
done
基本流程如上:
在执行过程中发现文件计数器FILENUM总是有还原成默认值的情况。
经过调试发现,每一次while read line 循环的文件完成之后都会发生这种现象。
启动sh的时候同时也发现了两个同名的*.sh进程
经过查阅资料,发现在while read line 的用法中常用的有两种。
cat FILE | while read line
do
`
done
while read line
do
done < FILE
经过分别测试得出以下结论:
使用管道符 | 的方法相当于启动了一个独立的子进程,因此循环中的变量FILENUM是属于自进程中的,与循环外的FILENUM虽然同名,但是值却不同。
使用重定向 < 的方法则不会有这种现象,在脚本启动时并没有子进程出现,因此循环内部变量FILENUM与循环外的FILENUM变量在同一个bash shell中。
#!/bin/bash
tmpfile=/root/multipath_tmp
[ -e "$tmpfile" ] && rm -rf $tmpfile
this_inode=$(ifconfig Mgnt-0 | grep "inet " | awk '{print $2}')
function explain_one_foreach () {
for lun in $(cat "$WWIDS" | grep -v ^# | sed s#/##g);
do
result=$(multipath -ll "$lun" 2> /dev/null)
echo "$result" | grep " sd" | awk -v nlun="$lun" '{print nlun" "$3" "$2" "$5" "$6" "$7}' >> $tmpfile
done
}
function explain_all () {
results=$(multipath -ll 2> /dev/null)
local lun=""
local count=0
echo "$results" | while read line;
do
if [ "${line:0:2}" == "36" ]; then
lun=$(echo $line | awk '{print $1}')
if [ ! -z "$last_lun" ] && [ "$count" -gt 0 ]; then
echo "$last_lun at $this_inode count is [$count]"
fi
last_lun=$lun
count=0
fi
if [ $(echo $line | grep -c " sd") -eq 1 ]; then
echo "$line" | awk -v nlun="$lun" '{print nlun" "$3" "$2" "$5" "$6" "$7}'
count=$((count+1))
fi
done
echo "$lun at $this_inode count is [$count]"
}
WWIDS=/etc/multipath/wwids
if [ ! -f /etc/multipath/wwids ]; then
echo "/etc/multipath/wwids files not existed"
if [ $(multipath -ll 2>&1 | grep -c "DM multipath kernel driver not loaded") -eq 1 ]; then
echo "DM multipath kernel driver not loaded"
exit 1
fi
fi
explain_all >> $tmpfile
exit 0
最后一行没有值 366c2222222222aa95116c76b00000163 sdc 33:0:0:2 active ready running 366c2222222222aa95116c76b00000163 sdg 34:0:0:2 active ready running 366c2222222222aa95116c76b00000163 sdk 35:0:0:2 active ready running 366c2222222222aa95116c76b00000163 sdo 36:0:0:2 active ready running 366c2222222222aa95116c76b00000163 at 2.2.2.2 count is [4] 366c2222222222aa95116c76b00000162 sdb 33:0:0:1 active ready running 366c2222222222aa95116c76b00000162 sdf 34:0:0:1 active ready running 366c2222222222aa95116c76b00000162 sdj 35:0:0:1 active ready running 366c2222222222aa95116c76b00000162 sdn 36:0:0:1 active ready running 366c2222222222aa95116c76b00000162 at 2.2.2.2 count is [4] 366c2222222222aa95116c76b00000165 sde 33:0:0:4 active ready running 366c2222222222aa95116c76b00000165 sdi 34:0:0:4 active ready running 366c2222222222aa95116c76b00000165 sdm 35:0:0:4 active ready running 366c2222222222aa95116c76b00000165 sdq 36:0:0:4 active ready running at 2.2.2.2 count is [0]
#!/bin/bash
tmpfile=/root/multipath_tmp
rstfile=/root/multipath_rst
[ -e "$tmpfile" ] && rm -rf $tmpfile
[ -e "$rstfile" ] && rm -rf $rstfile
this_inode=$(ifconfig Mgnt-0 | grep "inet " | awk '{print $2}')
function explain_one_foreach () {
for lun in $(cat "$WWIDS" | grep -v ^# | sed s#/##g);
do
result=$(multipath -ll "$lun" 2> /dev/null)
echo "$result" | grep " sd" | awk -v nlun="$lun" '{print nlun" "$3" "$2" "$5" "$6" "$7}' >> $rstfile
done
}
function explain_all () {
multipath -ll > $tmpfile 2> /dev/null
local lun=""
local count=0
while read line;
do
if [ "${line:0:2}" == "36" ]; then
lun=$(echo $line | awk '{print $1}')
if [ ! -z "$last_lun" ] && [ "$count" -gt 0 ]; then
echo "$last_lun at $this_inode count is [$count]"
fi
last_lun=$lun
count=0
fi
if [ $(echo $line | grep -c " sd") -eq 1 ]; then
echo "$line" | awk -v nlun="$lun" '{print nlun" "$3" "$2" "$5" "$6" "$7}'
count=$((count+1))
fi
done < $tmpfile
echo "$lun at $this_inode count is [$count]"
}
WWIDS=/etc/multipath/wwids
if [ ! -f /etc/multipath/wwids ]; then
echo "/etc/multipath/wwids files not existed"
if [ $(multipath -ll 2>&1 | grep -c "DM multipath kernel driver not loaded") -eq 1 ]; then
echo "DM multipath kernel driver not loaded"
exit 1
fi
fi
explain_all >> $rstfile
# cat $rstfile
exit 0
对了
366c2222222222aa95116c76b00000163 sdc 33:0:0:2 active ready running 366c2222222222aa95116c76b00000163 sdg 34:0:0:2 active ready running 366c2222222222aa95116c76b00000163 sdk 35:0:0:2 active ready running 366c2222222222aa95116c76b00000163 sdo 36:0:0:2 active ready running 366c2222222222aa95116c76b00000163 at 2.2.2.2 count is [4] 366c2222222222aa95116c76b00000162 sdb 33:0:0:1 active ready running 366c2222222222aa95116c76b00000162 sdf 34:0:0:1 active ready running 366c2222222222aa95116c76b00000162 sdj 35:0:0:1 active ready running 366c2222222222aa95116c76b00000162 sdn 36:0:0:1 active ready running 366c2222222222aa95116c76b00000162 at 2.2.2.2 count is [4] 366c2222222222aa95116c76b00000165 sde 33:0:0:4 active ready running 366c2222222222aa95116c76b00000165 sdi 34:0:0:4 active ready running 366c2222222222aa95116c76b00000165 sdm 35:0:0:4 active ready running 366c2222222222aa95116c76b00000165 sdq 36:0:0:4 active ready running 366c2222222222aa95116c76b00000165 at 2.2.2.2 count is [4]
https://www.cnblogs.com/Juststudy02/p/9842713.html