Remove Line Breaks with Sed

sed-remove-linebreaks.md

Remove Line Breaks with Sed

sed operates on lines, excluding the newline character, so it cannot directly remove newlines within a line using standard commands. The newline is stripped before processing and added back after. To remove or replace newlines, you need special techniques:

• Replace all newlines with spaces:

  sed -e ':a;N;$!ba;s/\n/ /g' file

  This reads the entire file into the pattern space and replaces all newlines with spaces.

• Remove all newlines (flatten to one line):

  sed -z 's/\n//g' file

  The -z option treats input as null-separated, allowing sed to process newlines as data.

• Remove only trailing newlines:

  sed -z '$ s/\n$//' file

  This removes the final newline, useful when preserving the POSIX text file standard.

• Remove newlines only between specific patterns (e.g., lines not ending with "):

  sed '/"$/{:a;N;s/\n//;ta}' file

  This appends lines until a line ends with " and removes newlines in between.

For simple cases, tr -d '\n' is often faster and more reliable than sed.