seek=$(($addr/4))
时间: 2024-02-18 14:03:19 浏览: 29
这段代码是一个shell脚本中的表达式,其中包含了一个算术运算符$(( ))和一个整数除法运算符/。该表达式的含义是将变量$addr的值除以4,得到的商赋给变量$seek。
在shell脚本中,$(( ))是一个算术运算符,可以进行各种算术运算,包括加减乘除、位运算、逻辑运算等。除法运算符/是整数除法运算符,只取整数部分的结果。
因此,该表达式的作用是将变量$addr的值转换为以4为单位的地址值。在某些场景下,需要将地址值转换为以字节为单位的值,可以将表达式改为:
```
byte_addr=$(($addr*4))
```
其中,变量$byte_addr表示以字节为单位的地址值,其值为变量$addr的值乘以4。
相关问题
start_addr=0x05877000 #end_addr=0x3ffff000 end_addr=0x05877002 data_write=0x55AA55AA data_read=$(printf "%08x" $data_write) count=0 match_count=0 for ((addr=$start_addr; addr<$end_addr; addr=addr+4)); do echo $data_write | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul done for ((addr=$start_addr; addr<$end_addr; addr+=4)); do data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"') if [ "$data_read" == "$data" ]; then match_count=$((match_count+1)) fi count=$((count+1)) done echo $data echo $data_read那么该如何修改程序才能让程序输出PASS
为了让程序输出 PASS,我们需要在循环结束后,判断 match_count 是否等于 count,如果等于,即所有数据都成功读取并且与写入的数据一致,就输出 PASS。
修改后的代码如下:
```
start_addr=0x05877000
end_addr=0x3ffff000
data_write=0x55AA55AA
data_read=$(printf "%08x" $data_write)
count=0
match_count=0
for ((addr=$start_addr; addr<$end_addr; addr=addr+4)); do
echo $data_write | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul
done
for ((addr=$start_addr; addr<$end_addr; addr+=4)); do
data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"')
if [ "$data_read" == "$data" ]; then
match_count=$((match_count+1))
fi
count=$((count+1))
done
if [ $match_count -eq $count ]; then
echo "PASS"
else
echo "FAIL"
fi
echo $data
echo $data_read
```
这样,当所有数据都成功读取并且与写入的数据一致时,程序就会输出 PASS。
start_addr=0x05877000 #end_addr=0x3ffff000 end_addr=0x05877002 data_write=0x55AA55AA data_read=$(printf "%08x" $data_write) count=0 match_count=0 for ((addr=$start_addr; addr<$end_addr; addr=addr+4)); do echo $data_write | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"') #percent=$(echo "scale=2; ($addr - $start_addr) * 100 / ($end_addr - $start_addr)" | bc) # echo -ne "Writing: $percent%\r" done # echo $data for ((addr=$start_addr; addr<$end_addr; addr+=4)); do data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"') if [ "$data_write" == "$data_read" ]; then match_count=$((match_count+1)) fi count=$((count+1)) # percent=$(echo "scale=2; $count * 100 / (($end_addr - $start_addr) / 4)" | bc) # echo -ne "Reading: $percent%\r" done #echo $data echo $data_read echo $data_write 如果data_read=55aa55aa,data_write=0x55AA55AA,那么该如何修改程序才能让程序输出PASS
要让程序输出PASS,需要将match_count与count进行比较。如果它们相等,说明所有写入的数据都被正确地读回,程序就可以输出PASS。因此,可以在第一个循环中,将写入数据的值改为data_read,即:
```
echo $data_read | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul
```
然后,在第二个循环中,添加一个判断语句,如果match_count等于count,则输出PASS,如下所示:
```
if [ $match_count -eq $count ]; then
echo "PASS"
fi
```
完整代码如下:
```
start_addr=0x05877000
end_addr=0x3ffff000
data_write=0x55AA55AA
data_read=$(printf "%08x" $data_write)
count=0
match_count=0
for ((addr=$start_addr; addr<$end_addr; addr=addr+4)); do
echo $data_read | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul
done
for ((addr=$start_addr; addr<$end_addr; addr+=4)); do
data=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"')
if [ "$data_read" == "$data" ]; then
match_count=$((match_count+1))
fi
count=$((count+1))
done
if [ $match_count -eq $count ]; then
echo "PASS"
fi
```