Answer by Xen2050 for convert txt file to csv seperated with tabs

A web search for "replace space with comma" was very fruitful, didn't that work out for you first? Would've found lots of answers like this:

tr ' ' ',' < input > output

or for tabs:

tr '\t' ',' < input > output

and

sed 's/\s\+/,/g' input > output

\s is the space class (like [:space:]) and should replace any runs (+ (escaped) = one or more of the preceding character) of spaces or tabs or newlines too. This next one would only replace each single space or tab with a single comma (like running both above tr's) :

sed 's/[ \t]/,/g' input > output

And -i edits the file in-place (directly edits the file) in sed

Here's a sed that will match a space-number or a number-space, and replace them with a comma, using the OR command/symbol | escaped as \| below:

sed 's/ [0-9]\|[0-9] /,/g'