Data Processing

How to remove trailing whitespace from a file

Learn how to remove trailing whitespace from a file using the sed command.

Summary

To remove any trailing whitespace from a file, we can use sed. By using in-place editing -i, sed can be provided with a search-and-replace action to filter out whitespace at the end of each line. By replacing it with nothing, it will effectively be removed.

sed -i 's/[[:space:]]*$//' mytextfile.txt

Explanation

  • -i = inline file edit
  • s/ = search
  • [[:space:]]*$ = search one or more occurences of whitespace just before the end of the line
  • // = No text, so any occurences of the whitespace will be emptied

The [[:space:]] is called a character class and refers to space characters. Normally this includes a tab, vertical tab, form feed, new line, carriage return, and of course a space.

How to insert a line at the beginning of a file

Learn how to insert a line of text at the beginning of a file using the sed command.

Summary

To insert a line at the beginning of a file, we can use sed to achieve this task. By using in-place editing -i, we can instruct sed to make a change to an existing file. The next step is to tell sed what to change or insert and at what place.

sed -i '1i # New first line' mytextfile.txt

Explanation

  • -i = inline file edit
  • 1i = insert at first line
  • # New first line = Text to add