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Old 01-21-2010, 01:10 AM   #1
masatheesh
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Difference between $HOSTNAME and $(hostname)


Can anyone please tell me the difference between $HOSTNAME and $(hostname)?
 
Old 01-21-2010, 01:13 AM   #2
Tinkster
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Sure.

$HOSTNAME is a shell variable.

$(hostname) runs the command 'hostname' in a sub-shell.
 
Old 01-21-2010, 01:59 AM   #3
masatheesh
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can you please tell me example for importance of these?

Thanks
 
Old 01-21-2010, 02:16 AM   #4
paulsm4
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Do you understand what Tinkster was trying to explain?

"$HOSTNAME" is just a variable.

"$(hostname)", in contrast, runs the program "hostname" and makes its contents (the string consisting of your computer's host name) available to the shell. One of the things you could do with it is assign those contents (the "hostname" string) to a new variable.
 
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Old 01-21-2010, 02:39 AM   #5
cantab
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Let us take another example.
Code:
[tw296@bevelle ~]$ DATE=Thursday # define a variable DATE
[tw296@bevelle ~]$ echo $DATE # display the variable we just defined
Thursday
[tw296@bevelle ~]$ echo $(date) # display the output of the command 'date' 
Thu Jan 21 07:37:23 GMT 2010
 
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Old 01-21-2010, 03:17 AM   #6
masatheesh
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Thanks a lot to everyone
 
  


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