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magic number in unix

Posted on 2000-02-22
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Last Modified: 2008-03-06
What is the magic number in unix???
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Question by:bolotin
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by:RobWMartin
ID: 2547078
It is a known sequence of bytes that always show up in a file of a certain type.  You can usually assume that if the sequence shows up in the right spot in the file, you have a file of the given type.  For example, if the file starts with 0x000001b3 it is an MPEG video stream.  The information is usually kept in a magic file.  The "file" command uses it to identify files.

Rob
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by:RobWMartin
ID: 2547100
BTW:  you can look at the contents of the magic file to find the magic numbers of well-known file types.  Since the location of the magic file depends on the flavor of *nix you are using, try

find / -name 'magic'

Then pipe the file through the more command to look at it.

Rob
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Accepted Solution

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cartoon022100 earned 50 total points
ID: 2550049
the file "/etc/magic" contains all magic numbers. the "file" command uses this magic number to compare with the contents in the file.depending upon the matching ,the file command gives output as ascii text  ot C file or binary file etc etc

"man magic" may help u more
Inigo
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Expert Comment

by:RobWMartin
ID: 2554760
The magic file is not located at /etc/magic on all systems.
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Expert Comment

by:RobWMartin
ID: 2616313
bolotin,

Hate to be pushy, but you need to decide who gave you the right answer first.  You can accept one of my comments as the answer, unless you feel cartoon gave you more useful info.
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