YouTipLinux Comm Dd
# Linux dd Command
[ Linux Command Manual](#)
The Linux `dd` command is used to read, convert, and output data.
`dd` can read data from standard input or a file, convert the data according to a specified format, and then output it to a file, device, or standard output.
**Parameter Description:**
* `if=file`: Input filename, default is standard input. Specifies the source file.
* `of=file`: Output filename, default is standard output. Specifies the destination file.
* `ibs=bytes`: Read `bytes` bytes at a time, i.e., specify a block size of `bytes` bytes.
* `obs=bytes`: Write `bytes` bytes at a time, i.e., specify a block size of `bytes` bytes.
* `bs=bytes`: Set both read/write block size to `bytes` bytes.
* `cbs=bytes`: Convert `bytes` bytes at a time, i.e., specify the conversion buffer size.
* `skip=blocks`: Skip `blocks` blocks from the beginning of the input file before starting to copy.
* `seek=blocks`: Skip `blocks` blocks from the beginning of the output file before starting to copy.
* `count=blocks`: Copy only `blocks` blocks, where the block size equals the number of bytes specified by `ibs`.
* `conv=`, where keywords can be any of the following 11:
* `conversion`: Convert the file using specified parameters.
* `ascii`: Convert from EBCDIC to ASCII.
* `ebcdic`: Convert from ASCII to EBCDIC.
* `ibm`: Convert from ASCII to alternate EBCDIC.
* `block`: Convert each line to a length of `cbs`, padding with spaces if insufficient.
* `unblock`: Pad each line to a length of `cbs` with spaces.
* `lcase`: Convert uppercase characters to lowercase.
* `ucase`: Convert lowercase characters to uppercase.
* `swap`: Swap every pair of input bytes.
* `noerror`: Do not stop on errors.
* `notrunc`: Do not truncate the output file.
* `sync`: Pad each input block to `ibs` bytes with NUL characters if insufficient.
* `--help`: Display help information.
* `--version`: Display version information.
### Examples
To create a bootable disk under Linux, you can use the following command:
```bash
dd if=boot.img of=/dev/fd0 bs=1440k
To convert all English letters in the file `testfile` to uppercase and output to `testfile_1`, use the following command at the command prompt:
```bash
dd if=testfile_2 of=testfile_1 conv=ucase
The content of `testfile_2` is:
```bash
$ cat testfile_2 #Content of testfile_2
HELLO LINUX!
Linux is a free unix-type opterating system.
This is a linux testfile!
Linux test
After conversion, the content of `testfile_1` is as follows:
```bash
$ dd if=testfile_2 of=testfile_1 conv=ucase #Use dd command for case conversion
0+1 records in
0+1 records out
95 bytes (95 B) copied, 0.000131446 s, 723 kB/s
cmd@hdd-desktop:~$ cat testfile_1 #View the converted content of testfile_1
HELLO LINUX!
LINUX IS A FREE UNIX-TYPE OPTERATING SYSTEM.
THIS IS A LINUX TESTFILE!
LINUX TEST
#All characters in testfile_2 have become uppercase
To read a string from the standard input device, convert it to uppercase, and then output it to the standard output device, use the following command:
```bash
dd conv=ucase
After entering the above command and pressing Enter, type a string, press Enter again, then press the key combination `Ctrl+D` to exit. The following result will appear:
```bash
$ dd conv=ucase
Hello Linux! #Type the string and press Enter
HELLO LINUX! #Press Ctrl+D to exit, showing the uppercase result
0+1 records in
0+1 records out
13 bytes (13 B) copied, 12.1558 s, 0.0 kB/s
[ Linux Command Manual](#)
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