[SFS] bash - things you can't do with backticks

Mon, 24 Mar 2014 09:24:08 -0600 (MDT)

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I always use something like this "$( expression )" to get "the output of expression", rather than backticks like this "` expression `" and teach others to do likewise for two reasons: It's more readable and it's nestable. But, when teaching, I can never come up with a good example of nesting, so today, I happen to have one. I want to delete all the files in this directory, except the newest three. 

rm $( ls -tr | head -n $(( $( ls -tr | wc -l ) - 3 ))) 

It has some big bugs and I cannot lie, but it does demonstrate nesting. 

-- 
David L. Willson 
Teacher, Engineer, Evangelist 
RHCE+Satellite CCAH Network+ A+ Linux+ LPIC-1 UbuntuCP NovellCLA 
Mobile 720-333-LANS(5267) 
http://sofree.us 

This is a good time for a r3VOLution. 

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>I always use something like this "$( expression )" to get "the output of e=
xpression", rather than backticks like this "` expression `"<span> and teac=
h others to do likewise for two reasons: It's more readable and it's nestab=
le. But, when teaching, I can never come up with a good example of nesting,=
 so today, I happen to have one. I want to delete all the files in this dir=
ectory, except the newest three.<br><br><br>rm $( ls -tr | head -n $(( $( l=
s -tr | wc -l ) - 3 )))<br><br></span><br><span id=3D"1db0e1d5-cb88-49a4-8e=
2f-e90f3b6109a8"><span id=3D"1db0e1d5-cb88-49a4-8e2f-e90f3b6109a8">It has s=
ome big bugs and I cannot lie, but it does demonstrate nesting.<br><br></sp=
an><span name=3D"x"></span>--<br>David L. Willson<br>Teacher, Engineer, Eva=
ngelist<br>RHCE+Satellite CCAH Network+ A+ Linux+ LPIC-1 UbuntuCP NovellCLA=
<br>Mobile 720-333-LANS(5267)<br>http://sofree.us<br><br>This is a good tim=
e for a r3VOLution.<span name=3D"x"></span><br></span><br></div></body></ht=
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