解决方法
你不能,但你可以使用一个文件来做到这一点
#!/bin/sh
# if we don't have a file,start at zero
if [ ! -f "/tmp/value.dat" ] ; then
value=0
# otherwise read the value from the file
else
value=`cat /tmp/value.dat`
fi
# increment the value
value=`expr ${value} + 1`
# show it to the user
echo "value: ${value}"
# and save it for next time
echo "${value}" > /tmp/value.dat
