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extract column based on name

 
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# 1  
Old 08-29-2007
extract column based on name
I need to extract a column from a tab delimited text file based on the string in the first row. (i.e. extract the column labeled "reaction_time"). I know that this can be done with awk by determining the column #, but I want to do it based on a search for the string b/c the column number changes for different subjects. Thanks for your help.
# 2  
Old 08-29-2007
can you provide one sample how your input file looks like that will be easy for us.

Thanks
# 3  
Old 08-29-2007
Code:
input.txt (tab delimited fields)
--------------------------------
Name	Surname	Age
AAA	aaa	20
BBB	bbb	25
CCC	ccc	30



nawk -v col="Surname" -F'\t' '
   {
      if (NR == 1) {
         for (i=1; i<=NF; i++) {
            if ($i == col) { colnum=i; break; }
         }
         if (! colnum) {
            print("Specified column does not exist!");
            exit;
         }
      } else {
         print($colnum);
      }
   }
' input.txt



Output
------
aaa
bbb
ccc

It's tested on Solaris, so you may substitute "nawk" with "gawk" or "awk" or whatever depending on your OS.
# 4  
Old 08-29-2007
Perfect. Many thanks.
 
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