How to remove the milliseconds from timestamps with sed?

Question

My input file is as follows:

12/13/2011,07:14:13.724,12/13/2011 07:14:13.724,231.56.3.245,LasVegas,US

I wish to get the following:

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Answer 1

You were near but some characters are special in sed (in my version, at least): {, }, (, ), but not :. So you need to escape them with a back-slash.

And \1 takes expression between paretheses, it should be the first part until seconds, not the second one.

A modification of your version could be:

sed "s/\([0-9]\{2\}:[0-9]\{2\}:[0-9]\{2\}\)\.[0-9]\{1,3\}/\1/g" input_file.csv > output.csv