求如何打印任意文本正中间行

oldknew

求打印任意文本正中间行，奇数行文本打印正中间行，偶数行文本打印正中间两行，如
[aii@localhost gjy]$ cat -n 1.dat
     1        fjfjjgfjg:fjdjfjdf:20140214:fjd
     2        fjfjjgfjg:fjdjfjdf:20140214:fjd
     3        fjfjjgfjg:fjdjfjdf:20140214:fjd
     4        fjfjjgfjg:fjdjfjdf:20150325:fjd
     5        fjfjjgfjg:fjdjfjdf:20160324:fjd
     6        fjfjjgfjg:fjdjfjdf:20140214:fjd
     7        fjfjjgfjg:fjdjfjdf:20140214:fjd
     8        fjfjjgfjg:fjdjfjdf:20110529:fjd
     9        fjfjjgfjg:fjdjfjdf:20040919:fjd
    10        fjfjjgfjg:fjdjfjdf:20140214:fjd
    11        fjfjjgfjg:fjdjfjdf:20140214:fjd
    12        fjfjjgfjg:fjdjfjdf:20140214:fjd
打印出
             fjfjjgfjg:fjdjfjdf:20140214:fjd
             fjfjjgfjg:fjdjfjdf:20140214:fjd
两行

[aii@localhost gjy]$ cat -n 1.log
     1        1.txt
     2        2.txt
     3        a.txt
     4        b.txt
     5        c.txt
     6        random1245.txt
     7        random1_6.txt
     8        select_result.txt
     9        select.txt
    10        snm.txt
    11        zhongwen.txt
打印出
random1245.txt
一行

sunzhiguolu

回复 1# oldknew

1. perl -ne '{push(@a,$_)}END{$n=int(@a/2);print @a%2?$a[$n+1]:@a[$n-1,$n]}' urfile
   

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oldknew

感谢大神！不过perl本人还没怎么学，目前只会一点shell

oldknew

试了一下偶数行的文本，貌似返回的不对呢

moperyblue

1. wc -l 1.*
   
2. 12 1.dat
   
3. 11 1.log
   
4. 23 总用量
   
5. 
   
6. awk 'BEGIN{while(getline x < ARGV[1])a[++i]=x}END{if(i%2)print a[int(i/2)+1];else print a[i/2] RS a[i/2+1]}' 1.dat
   
7. 6        fjfjjgfjg:fjdjfjdf:20140214:fjd
   
8. 7        fjfjjgfjg:fjdjfjdf:20140214:fjd
   
9. 
   
10. awk 'BEGIN{while(getline x < ARGV[1])a[++i]=x}END{if(i%2)print a[int(i/2)+1];else print a[i/2] RS a[i/2+1]}' 1.log
    
11. 6        random1245.txt
    
12. 
    
13. awk 'BEGIN{while(getline x < ARGV[1])++i}i%2==1&&NR==int(i/2)+1||i%2==0&&(NR==i/2||NR==i/2+1)' 1.dat

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sunzhiguolu

回复 4# oldknew
再试下, 应该没啥问题了.

   

oldknew

好的，谢谢

jason680

回复 1# oldknew

$ seq 5 | awk '{a[NR]=$0}END{m=int(++NR/2);print NR%2?a[m]"\n"a[m+1]:a[m]}'
3

$ seq 6 | awk '{a[NR]=$0}END{m=int(++NR/2);print NR%2?a[m]"\n"a[m+1]:a[m]}'
3
4

   

oldknew

哇，这条是不是需要事先知道总行数的？