DUMP_CMD="mysqldump -u${USER} -p${PASS} ${DB} > ${BACKUP_DIR}/${DB}_${DATE}.sql"解释
时间: 2023-11-01 20:28:06 浏览: 26
这是一行代码,其中使用了变量${USER},${PASS},${DB}和${DATE}来导出一个MySQL数据库的备份文件到指定的目录${BACKUP_DIR}中。具体的命令是mysqldump,-u指定用户名,-p指定密码,${DB}指定要备份的数据库名称,>指定将备份数据写入指定的文件名${DB}_${DATE}.sql中。
相关问题
start_addr=0x05877000 #end_addr=0x3ffff000 end_addr=0x05877002 data_write=0x55AA55AA data_read=$(printf "%08x" $data_write) count=0 match_count=0 for ((addr=$start_addr; addr<$end_addr; addr=addr+4)); do echo $data_write | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/nul data=$(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 $count ]; then
echo "PASS"
fi
```
start_addr=0x30000000 end_addr=0x30000003 data_write=0x55AA55AA count=0 match_count=0 # 写入数据 for ((addr=$start_addr; addr<$end_addr+1; addr=addr+1)); do echo -ne "\x55\xAA\x55\xAA" | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/null data=$(echo -ne "\x55\xAA\x55\xAA" | hexdump -e '/4 "%08x\n"') echo "data: $data" data_read=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | hexdump -e '/4 "%08x\n"') echo "data_read: $data_read" if [ "$data_read" == "$data" ]; then match_count=$((match_count+1)) echo "match_count: $match_count" fi count=$((count+1)) echo "count: $count" done # 输出结果 # 判断结果 if [ $match_count -eq $count ]; then echo "PASS" else echo "FAIL" fi 为什么这段代码data和data_read输出的都是空白?
这段代码中,数据写入和读取操作都使用了`dd`命令和`hexdump`命令。但是,`dd`命令和`hexdump`命令都是用于二进制数据的传输和显示,而不是文本数据。因此,如果想要在终端中查看二进制数据,需要使用`xxd`命令或者`od`命令。所以,将`hexdump`命令替换成`xxd`命令或者`od`命令即可输出正确的数据。
修改后的代码如下:
```
start_addr=0x30000000 end_addr=0x30000003 data_write=0x55AA55AA count=0 match_count=0
# 写入数据
for ((addr=$start_addr; addr<$end_addr+1; addr=addr+1)); do
echo -ne "\x55\xAA\x55\xAA" | dd of=/dev/mem bs=4 count=1 seek=$(($addr/8)) conv=notrunc 2>/dev/null
data=$(echo -ne "\x55\xAA\x55\xAA" | xxd -p)
echo "data: $data"
data_read=$(dd if=/dev/mem bs=4 count=1 skip=$(($addr/4)) 2>/dev/null | xxd -p)
echo "data_read: $data_read"
if [ "$data_read" == "$data" ]; then
match_count=$((match_count+1))
echo "match_count: $match_count"
fi
count=$((count+1))
echo "count: $count"
done
# 判断结果
if [ $match_count -eq $count ]; then
echo "PASS"
else
echo "FAIL"
fi
```