用法：dd [操作數(shù)] ...
或：dd 選項(xiàng)
Copy a file, converting and formatting according to the operands.
| command | english | 中文 |
|---|---|---|
| bs=BYTES | read and write up to BYTES bytes at a time | 讀或?qū)懙淖止?jié)數(shù) |
| cbs=BYTES | convert BYTES bytes at a time | 轉(zhuǎn)換的字節(jié)數(shù) |
| conv=CONVS | convert the file as per the comma separated symbol list | |
| count=N | copy only N input blocks | 輸入的塊數(shù) |
| ibs=BYTES | read up to BYTES bytes at a time (default: 512) | 每次讀取的字節(jié)數(shù) |
| if=FILE | read from FILE instead of stdin | 輸入的文件 默認(rèn)為stdio |
| iflag=FLAGS | read as per the comma separated symbol list | d |
| obs=BYTES | write BYTES bytes at a time (default: 512) | 寫的bytes 默認(rèn)為512B |
| of=FILE | write to FILE instead of stdout | 輸出文件 默認(rèn)為stdout |
| oflag=FLAGS | write as per the comma separated symbol list | |
| seek=N | skip N obs-sized blocks at start of output | skip N個(gè)塊輸出時(shí) |
| skip=N skip N ibs-sized blocks at start of input | 跳過(guò) N個(gè)塊輸入時(shí) | |
| status=LEVEL | The LEVEL of information to print to stderr; 'none' suppresses everything but error messages,'noxfer' suppresses the final transfer statistics, 'progress' shows periodic transfer statistics |
N and BYTES may be followed by the following multiplicative suffixes:
c =1, w =2, b =512, kB =1000, K =1024, MB =10001000, M =10241024, xM =M
GB =100010001000, G =102410241024, and so on for T, P, E, Z, Y.
-
Each CONV symbol may be:
ascii from EBCDIC to ASCII
ebcdic from ASCII to EBCDIC
ibm from ASCII to alternate EBCDIC
block pad newline-terminated records with spaces to cbs-size
unblock replace trailing spaces in cbs-size records with newline
lcase change upper case to lower case
ucase change lower case to upper case
sparse try to seek rather than write the output for NUL input blocks
swab swap every pair of input bytes
sync pad every input block with NULs to ibs-size; when used
with block or unblock, pad with spaces rather than NULs
excl fail if the output file already exists
nocreat do not create the output file
notrunc 不截?cái)噍敵鑫募?br> noerror 讀取數(shù)據(jù)發(fā)生錯(cuò)誤后仍然繼續(xù)
fdatasync 結(jié)束前將輸出文件數(shù)據(jù)寫入磁盤
fsync 類似上面，但是元數(shù)據(jù)也一同寫入 -
FLAG 符號(hào)可以是：
append 追加模式(僅對(duì)輸出有意義；隱含了conv=notrunc)
direct 使用直接I/O 存取模式
directory 除非是目錄，否則 directory 失敗
dsync 使用同步I/O 存取模式
sync 與上者類似，但同時(shí)也對(duì)元數(shù)據(jù)生效
fullblock 為輸入積累完整塊(僅iflag)
nonblock 使用無(wú)阻塞I/O 存取模式
noatime 不更新存取時(shí)間
nocache 丟棄緩存數(shù)據(jù)
noctty 不根據(jù)文件指派控制終端
nofollow 不跟隨鏈接文件
count_bytes treat 'count=N' as a byte count (iflag only)
skip_bytes treat 'skip=N' as a byte count (iflag only)
seek_bytes treat 'seek=N' as a byte count (oflag only)
Sending a USR1 signal to a running 'dd' process makes it
print I/O statistics to standard error and then resume copying.
$dd if=/dev/zero of=/dev/null& pid=$!
$ kill -USR1 $pid; sleep 1; kill $pid
18335302+0 records in
18335302+0 records out
9387674624 bytes (9.4 GB) copied, 34.6279 seconds, 271 MB/s
Options are:
--help 顯示此幫助信息并退出
--version 顯示版本信息并退出
GNU coreutils online help: http://www.gnu.org/software/coreutils/
請(qǐng)向http://translationproject.org/team/zh_CN.html 報(bào)告dd 的翻譯錯(cuò)誤
要獲取完整文檔，請(qǐng)運(yùn)行：info coreutils 'dd invocation'
[root@localhost text]# dd if=/dev/zero of=/data/text.txt bs=1M count=1
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.006107 seconds, 172 MB/s
//以上命令可以看出dd命令來(lái)測(cè)試內(nèi)存操作速度
[root@localhost text]# du -sh /data/text.txt
1.1M sun.txt
