[GRASS-dev] Re: [GRASS GIS] #181: tac command missing in OSX

[GRASS GIS]

#181: tac command missing in OSX
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  Reporter:  kyngchaos  |       Owner:  grass-dev at lists.osgeo.org
      Type:  defect     |      Status:  new                      
  Priority:  minor      |   Milestone:  6.3.1                    
 Component:  default    |     Version:  6.3.0                    
Resolution:             |    Keywords:  v.in.garmin, v.in.mapgen 
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Comment (by glynn):

 > > How about testing for the -r flag, as I mentioned?
 >
 > I'd recommend to check for the existence of `tac` instead,

 Agreed.

 > like (untested):

 I suggest either using "type", or just running e.g. "tac < /dev/null" and
 checking for an error. Scanning the path is problematic; it doesn't allow
 for shell built-ins or aliases, may not allow for extensions on Windows,
 etc.

 That still doesn't solve the issue of what to do if the system has neither
 tac nor "tail -r", neither of which are mandated by POSIX/XPG/SUS.

 Off the top of my head, the only thing that I can think of is to prefix
 each line with the line number using e.g. awk, use "sort -r", then strip
 the line numbers.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/181#comment:5>
GRASS GIS <http://grass.osgeo.org>