sed BSD/macOS Sed vs. GNU Sed vs. the POSIX Sed specification Append literal text to a line with function 'a'
Example
Note: For brevity, the commands use here-strings (<<<) and ANSI C-quoted strings ($'...'). Both these shell features work in bash, ksh, and zsh.
# GNU Sed
$ sed '1 a appended text' <<<'line 1'
line 1
appended text
# BSD Sed (multi-line form)
sed '1 a\
appended text' <<<'line 1'
# BSD Sed (single-line form via a Bash/Ksh/Zsh ANSI C-quoted string)
sed $'1 a\\\nappended text' <<<'line 1'
Note how BSD Seed requires a \ followed by an actual newline to pass the text to append.
The same applies to the related i (insert) and c (delete and insert) functions.
