shutdown command

[PleegWat]

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On 02/14/2012 06:15 PM, Ioannis Vranos wrote:
> On Tue, Feb 14, 2012 at 12:58 PM, Chris Green <cl at isbd.net> wrote:
>> The command line shutdown command has been around since the early
>> days of Unix.  Many other commands are just different ways of
>> calling it.
>> 
>> Looking at /sbin it seems that halt and poweroff are symbolic
>> links to reboot but shutdown is actually different.  However the
>> man page for reboot says that (except for some specific options)
>> reboot calls shutdown.
>> 
>> So basically it's shutdown at the bottom of all these commands.
> 
> I can't understand the following. poweroff and halt, are symbolic 
> links of /sbin/reboot. How all 3 have different outcome (poweoff, 
> halt, and reboot respectively)?

An executable can detect what name was used to invoke it. When using a
symbolic link, the name of the link (rather than its target) is used.

So basically, reboot does one thing if it was invoked as reboot,
another when invoked as halt, and a third when invoked as poweroff.

PleegWat

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