Definitions for dd
This page provides all possible meanings and translations of the word dd
Doctor of Divinity, DD(noun)
a doctor's degree in religion
dd is a command on Unix and Unix-like operating systems whose primary purpose is to convert and copy a file. On Unix, device drivers for hardware and special device files appear in the file system just like normal files; dd can also read from these files. As a result, dd can be used for tasks such as backing up the boot sector of a hard drive, and obtaining fixed amount of random data. The dd program can also perform conversions on the data as it is copied, including byte order swapping and conversion to and from the ASCII and EBCDIC text encodings. The name dd may be an allusion to the DD statement found in IBM's Job Control Language, where the initialism stands for "Data Description." The command's syntax resembles the JCL statement more than it does other Unix commands, so the syntax may have been a joke. Another explanation for the command's name is that "cc" was already taken by the C compiler. The dd command is specified by IEEE Std 1003.1-2008, which is part of the Single UNIX Specification.
The New Hacker's Dictionary
[Unix: from IBM JCL] Equivalent to cat or BLT. Originally the name of a Unix copy command with special options suitable for block-oriented devices; it was often used in heavy-handed system maintenance, as in “Let's dd the root partition onto a tape, then use the boot PROM to load it back on to a new disk”. The Unix dd(1) was designed with a weird, distinctly non-Unixy keyword option syntax reminiscent of IBM System/360 JCL (which had an elaborate DD ‘Dataset Definition’ specification for I/O devices); though the command filled a need, the interface design was clearly a prank. The jargon usage is now very rare outside Unix sites and now nearly obsolete even there, as dd(1) has been deprecated for a long time (though it has no exact replacement). The term has been displaced by BLT or simple English ‘copy’.
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