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Need to delete previous line after successful seearch

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# 1  
Old 10-30-2006
Need to delete previous line after successful seearch
i have a file in following pattreen

A:
Size = 10
B:
Size = 0
C:
Size = 220
D:
Size = 0

i want to Display only Charecters which have which have Size = 0

The Out put Should be
B:
D:

Can Some one Help
# 2  
Old 10-30-2006
Try...
Code:
$ cat file1
A:
Size = 10
B:
Size = 0
C:
Size = 220
D:
Size = 0

$ paste - - < file1
A:      Size = 10
B:      Size = 0
C:      Size = 220
D:      Size = 0

$ paste - - < file1 | awk '$NF == 0 { print $1 }'
B:
D:

# 3  
Old 10-30-2006
Hi Yogor

Can you please tell me what exactly paste - - < file1 means ?
although i see the out put you have mention still i am confusing the functionality of
- - ?? (double hyphen )
# 4  
Old 10-30-2006
nawk -f pb.awk myFile.txt

pb.awk:
Code:
!(FNR%2) && $NF == 0 { print a;next}
{a=$0}

# 5  
Old 10-30-2006
Code:
sed -n "N;/Size *= *0/{P;d;}" file

# 6  
Old 10-30-2006
Python alternative,simpler to understand
Code:
#!/usr/bin/python
data = open("input.txt").readlines()
for i in range(len(data)):
 	if data[i].startswith("Size = 0"):
 		print data[i-1].strip()

output:
Code:
B:
D:

# 7  
Old 10-31-2006
hi anbu can u explain this " sed -n "N;/Size *= *0/{P;d;}" "
hi anbu

can u explain this " sed -n "N;/Size *= *0/{P;d;}" "
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