Wednesday, September 29, 2010

SED instead of AWK

Some days ago I was presented with the following problem:
Two days ago I was confronted with a simple task: We have around 50 CSV files that should be concatenated into one file. Every file has a header at the first line that should be eliminated except for the first one.
My solution was to use AWK. Although my practical experience with SED is very limited I knew since the beginning that the problem could be solved with the SED editor. Today, six days after the AWK solution I found this SED solution:

sed -n '1p;/^set,/d;p' *.csv > all

The first sentence of the SED program print the first line of the input stream then continues with the second sentence that deletes a line when it contains the header, the magic here is that the d command stop processing the rest of the program's lines and start the program again reading the next line from the input stream, the last sentence always print the line.

After the first solution I found this one which is simpler, I should devote more time to SED's study!

sed -n '1p;/^set,/!p' *.csv > all

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