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Old 07-12-2009, 01:33 PM   #1
doru
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cut and sort incompatible


Code:
chkconfig --list | sort -k5,5r -k1,1 | cut -f1,5
works fine, but:
Code:
chkconfig --list | cut -f1,5 | sort -k2,2r -k1,1
does not sort by field 1.

Please pop up any idea.
 
Old 07-12-2009, 02:41 PM   #2
Disillusionist
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Removed.

Last edited by Disillusionist; 07-12-2009 at 02:48 PM.
 
Old 07-12-2009, 04:59 PM   #3
norobro
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It's a problem with delimiters. "sort" uses space(or consecutive spaces) and "cut" uses tab. The chkconfig output has no tab between the program name and the first on/off field.

Try these two commands:
Code:
chkconfig --list | sort  -t $'\t' -k5,5r -k1,1 | cut -f1,5
Code:
chkconfig --list |cut -f1,5 | sort -t $'\t' -k2r -k1,1
They make "sort" behave like "cut". I don't know how to make cut use multiple spaces as a delimiter. Maybe someone else does.

You can use awk instead of cut:
Code:
chkconfig --list |  awk '{printf("%-15s\t%s\n",$1,$5)}' |sort -k2r -k1,1
Code:
chkconfig --list | sort  -k5,5r -k1,1 | awk '{printf("%-15s\t%s\n",$1,$5)}'
 
Old 07-13-2009, 05:26 AM   #4
H_TeXMeX_H
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I don't know what the output of chkconfig might look like, so I can't test this.
 
Old 07-13-2009, 11:02 AM   #5
doru
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norobro: Thank you for your help. You are right, it is a matter of delimiters and your examples are great.

One can display hidden characters in a file with vi file and :set list (:set nolist). spaces are always displayed as spaces, tabs are displayed either as alignment (nolist), or as ^I (list).

chkconfig --list inserts both spaces and then tabs after names, either of them just fine for correct alignment.

sort splits fields between a non-blank character to the left and a blank character to the right. blanks are spaces and tabs. cut splits fields at tabs. What happens here is that all spaces and tabs after names in chkconfig --list are preserved by cut and assigned to the second field by sort. Therefore, when I sort -k2,2r, all "on" fields are not equal at all, they are sorted according to their leading spaces. The 'incompatibility' between cut and sort is that cut's delimiter is tab and therefore it assigns blanks to the left field, while sort's delimiter is space and it assigns them to the right one.

Last edited by doru; 07-25-2009 at 09:46 AM. Reason: correction
 
  


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