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Reverse even lines

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# 1  
Old 10-30-2013
Reverse even lines
I'm trying to reverse every even line in my file using the awk command below but it prints only the odd lines but nothing else:

Code:
$ awk '(NR % 2) {print}; !(NR % 2) {print | "rev";}' myfile

Any idea what I might have done wrong?

Thank you.
Last edited by Scrutinizer; 10-30-2013 at 06:23 PM.. Reason: Added code tags
# 2  
Old 10-30-2013
Quote:
Originally Posted by ivpz
I'm trying to reverse every even line in my file using the awk command below but it prints only the odd lines but nothing else:

$ awk '(NR % 2) {print}; !(NR % 2) {print | "rev";}' myfile

Any idea what I might have done wrong?

Thank you.
Show input and expected output
# 3  
Old 10-30-2013
Input:

Code:
@MVM-RI-I124161:36:000000000-A326L:1:1101:14597:1343 1:N:0:NTTACTCG
TCAGCGAAAACGCTTCGGAATGGAGGATATCTATTTTCCAAAATCCTCTGTGGTCTTTTTGCAGCATTCTGGAAAAAGACCACAGAGGATTTTGGAAAATAGATATATTTAATGGAGGCAAGTGTGAAAAATCACATTGAAATGCA
+
>>111>1111B1AEFE?000ACB10?0FBFGHCHHHHGFFD1CFECGGFFFFBFFGGHHH?A21B0EGGHEE1B100//E>0?/010/0FGGGD/1@10B1@1FDGBDGH2>F2110AEEAFGFHBFHBDAFGFGFGHBGFBGBFF


Output:
Code:
@MVM-RI-I124161:36:000000000-A326L:1:1101:14597:1343 1:N:0:NTTACTCG
ACGTAAAGTTACACTAAAAAGTGTGAACGGAGGTAATTTATATAGATAAAAGGTTTTAGGAGACACCAGAAAAAGGTCTTACGACGTTTTTCTGGTGTCTCCTAAAACCTTTTATCTATAGGAGGTAAGGCTTCGCAAAAGCGACT
+
FFBGBFGBHGFGFGFADBHFBHFGFAEEA0112F>2HGDBGDF1@1B01@1/DGGGF0/010/?0>E//001B1EEHGGE0B12A?HHHGGFFBFFFFGGCEFC1DFFGHHHHCHGFBF0?01BCA000?EFEA1B1111>111>>

Thanks.
Moderator's Comments:
Mod Comment
Please use code tags when posting data and code samples!
Last edited by vgersh99; 10-30-2013 at 05:58 PM.. Reason: code tags, please!
# 4  
Old 10-30-2013
Code:
 awk '!(FNR%2) {t="";l=length;for(i=1;i<=l;i++) t=substr($0,i,1) t;$0=t}1' myFile

# 5  
Old 10-30-2013
Quote:
Originally Posted by vgersh99
Code:
 awk '!(FNR%2) {t="";l=length;for(i=1;i<=l;i++) t=substr($0,i,1) t;$0=t}1' myFile

This is doing the trick but any idea why my command doesn't work? And can you please explain your command? Thank you.
# 6  
Old 10-30-2013
Code:
$ cat input
1
1 2
1 2 3
1 2 3 4

$ awk '(NR % 2 == 0)  { print }' input
1 2
1 2 3 4

$ awk '(NR % 2 == 1)  { print }' input
1
1 2 3

# 7  
Old 10-30-2013
Try

Code:
$ awk  '{if(NR%2==0)print $0 | "rev" ;else print }' file
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