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Combining columns from different files

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# 1  
Old 09-10-2009
Combining columns from different files

I have two files I need to combine. The problem I'm having is I need to only combine data from the second file in the empty spaces of the first. For example:

Data Field

Data Field
Data Field

Data Field

a - Insert Data
b - Insert Data
c - Insert Data
d - Insert Data
e - Insert Data
f - Insert Data

Output file
Data Field
b - Insert Data
Data Field
Data Field
e - Insert Data
Data Field

I'm thinking of awk but I'm not sure on where to start. I would appreciate if someone could direct me on where I can learn more on how to do this.
# 2  
Old 09-10-2009
This might work...

awk 'NF=0{print NR}' file1 >> blank_line_numbers
for i in `cat blank_line_numbers`
insert_line=`head -$i file2 | tail -1`
sed 's/^$/$insert_line/$i' file1 >> temp
mv temp file1

# 3  
Old 09-11-2009

You can try the following bash script.

export PATH

exec 3<file1
exec 4<file2

while read a 0<&3; do
        read b 0<&4
        echo ${a:-$b}

# this line will output any remaining lines in file2
# if you don't need this, then you can take it out
cat <&4

Last edited by rwu; 09-11-2009 at 03:49 AM..
# 4  
Old 09-11-2009
I try to resolve this with command awk, but i have problems...
I try this...
awk 'NR==FNR{a[NR]=$0;next}{b[FNR]=$0}END { for(i=1;i<=FNR;i++) if (b[i]=" ") b[i]=a[i]}{print i,b[i]}' file1 file2

please advice.
# 5  
Old 09-11-2009
nawk 'FNR==NR {f1[FNR]=$0;next} {print NF?$0:f1[FNR]}' file2 file1

# 6  
Old 09-11-2009
great, magic...but i don't understand this part....

nawk 'FNR==NR {f1[FNR]=$0;next} {print NF?$0:f1[FNR]}'

Could you explain please .....

# 7  
Old 09-11-2009
Originally Posted by protocomm
great, magic...but i don't understand this part....

nawk 'FNR==NR {f1[FNR]=$0;next} {print NF?$0:f1[FNR]}'

Could you explain please .....

you can rewrite this as:
nawk 'FNR==NR {f1[FNR]=$0;next} 
                           if (NF!=0) 
                              print $0
                              print f1[FNR]
                        }' file2 file1

Last edited by vgersh99; 09-11-2009 at 03:08 PM..

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