I am using cygwin and have a lot of files in which I want to convert tabs to spaces (four spaces per tab) and remove all space characters that exist at end of line. Is there a utility for this in Linux?
1 Answer
sed is your friend for that. Comes for free with all Linux distros, as far as I know. It's the "Stream EDitor", and works with regular expressions. To apply it to your example:
sed -E 's/\t/ /g;s/\s*($)/\1/g' infile outfile
Each tab (\t) is replaced by 4 spaces, and trailing spaces (actually, all whitespace characters up to the end of the line ($) are removed. If you don't want the result in a new file, you can tell sed to do the replacements inline (-i):
sed -i -E 's/\t/ /g;s/\s*($)/\1/g' file
In a lot of files? No prob:
sed -i -E 's/\t/ /g;s/\s*($)/\1/g' *
(just pass a "mask", like *.txt or whatever files should be matched).
You can get sed from your distro's package management, e.g. apt install sed.
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What language is 's/\t/ /g;s/\s*($)/\1/g'? Is that a regular expression? I don't see the digit 4 anywhere in the regular expression. What is going on here? Jun 24, 2021 at 15:02
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Yes, it's regular expression. And no, the question wasn't asking for digits – but the replacement part has 4 spaces as requested. Just try it out with some sample files (I did, and it does what you asked for). The trailing
/gmakes sure it's applied Globally, so all tabs are replaced by 4 spaces each.– Izzy ♦Jun 25, 2021 at 7:20 -
I am just curious to know, how did you specify the "4 spaces" part? Jun 25, 2021 at 10:42
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By using 4 spaces? The big gap following the
\t/are 4 spaces.sedsyntax iss/<RegExToMatch>/<replacement>/<op>, basically meaningsearch for this<RegEx>and replace it according to<replacement>applying<op>. You can concatenate multiple operations using a;. So taking the first part, it meanssearch for a\tab, replace it by 4 spaces,globally. The second part issearch for white-\spaces up to the EOL ($) and replace that with the EOL (back reference:\1is the first(match)).– Izzy ♦Jun 25, 2021 at 21:13
sed