Linux in a Nutshell, Fifth Edition

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Chapter 3: Linux Commands

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

ibs=n

Set input block size to n bytes (default is 512).

if=file

Read input from file (default is standard input).

obs=n

Set output block size to n bytes (default is 512).

of=file

Write output to file (default is standard output).

seek=n

Skip n output-sized blocks from start of output file.

skip=n

Skip n input-sized blocks from start of input file.

--help

Print help message and then exit.

--version

Print the version number and then exit.

You can multiply size values (n) by a factor of 1024, 512, or 2 by

appending the letter k, b,orw, respectively. You can use the letter

x as a multiplication operator between two numbers.

Examples

Convert an input file to all lowercase:

dd if=caps_file of=small_file conv=lcase

Retrieve variable-length data and write it as fixed-length to out:

[data_retrieval_cmd] | dd of=out conv=sync,block

deallocvt

deallocvt N

Deallocate and destroy the unused virtual console /dev/ttyN.

Multiple consoles may be named with additional spaces and inte-

gers: deallocvt 1 4 will deallocate the /dev/tty1 and /dev/tty4

consoles. Consoles are considered unused if they are not in the

foreground, have no open processes, and have no selected text. The

command will not destroy consoles that are still active.

debugfs

debugfs [[option] device]

System administration command. ...