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Which

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'''which''' is a very useful system command used to find out exactly what is going to get executed when you ask for a command without specifying a path.  For instance, the [[csh]] shell has a [[built-in]] function called [[time]], but there is also a version at '''/usr/bin/time'''.  So '''which''' one gets executed if you simply type "time"?
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'''which''' is a very useful system command used to [[find]] out exactly what is going to get executed when you ask for a command without specifying a path.  For instance, the [[csh]] shell has a [[built-in]] function called [[time]], but there is also a version at '''/usr/bin/time'''.  So '''which''' one gets executed if you simply type "time"?
  
  '''ph34r#''' which time
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  ph34r#''' which time'''
'''time: shell built-in command.'''
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time: shell built-in command.
  '''ph34r#'''
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  ph34r#
  
 
This is particularly useful to know in the case of the [[time]] command above, because [[csh]]'s [[built-in]] "time" does not have the same featureset described in the [[man]] page for [[time]], which is based on the version to be found at '''/usr/bin/time'''.  
 
This is particularly useful to know in the case of the [[time]] command above, because [[csh]]'s [[built-in]] "time" does not have the same featureset described in the [[man]] page for [[time]], which is based on the version to be found at '''/usr/bin/time'''.  

Latest revision as of 13:44, 19 November 2007

which is a very useful system command used to find out exactly what is going to get executed when you ask for a command without specifying a path. For instance, the csh shell has a built-in function called time, but there is also a version at /usr/bin/time. So which one gets executed if you simply type "time"?

ph34r# which time
time: shell built-in command.
ph34r#

This is particularly useful to know in the case of the time command above, because csh's built-in "time" does not have the same featureset described in the man page for time, which is based on the version to be found at /usr/bin/time.

See also where for figuring out how many different versions of the same command or file you have strewn throughout your path.

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