dd — Convert and copy a file.


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dd — Convert and copy a file.


‘dd’ copies and optionally converts data with changeable I/O block
size. Reads are issued to the input file or device for the size of
the input buffer and writes are issued for the size of the output
buffer. This allows I/O requests to be tailored to the requirements of
a task. Output to standard error reports the number of full and short
blocks read and written.


$ dd if=/dev/urandom of=ddfile bs=1 count=100 — Dump random bytes in
        the file.

$ dd if=/dev/zero of=/dev/fd0 — Format a floppy disk

$ dd if=/dev/fd0 of=/tmp/floppy.image — Take floppy disk image.

$ echo “12345678901234567890” | dd bs=1 skip=5 count=10 — Skip 5
     bytes in input and output only 10 Bytes.

$ echo “hello world” | dd cbs=1 conv=unblock — Take one byte at a

time and dump it in stdout with a new line.

$ echo “hello world” | dd conv=ucase — Change to Upper case.

$ echo “HELLO WORLD” | dd conv=lcase — Change to Lower case.

$ echo “12345678901234567890” > ddfile — Dummy file.

$ echo “AAAAAAA” | dd bs=1 seek=5 of=ddfile count=5 conv=notrunc —

Seek 5 bytes in output file and copy only 5 from input to output file.

NOTE: Instead of echo command, You can use some file in ‘if=’.

Read: man dd

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