Placing every character on a new line

Question

I have a file like this:

This is a sentence. This is another sentence. 

I need to put a new line after each character, such that only one character appears on every line, e.g.:

T h i s  i s  a  s e n t e n c e . T h i s  i s  a n o t h e r  s e n t e n c e . 

• The file is in UTF-8 and contains many non-English characters.
• It does not matter if spaces or carriage returns have their own line.

How can I remove every character to a new line?

Answer 1

Using sed replace every character with itself followed by a newline:

sed 's/./\0\n/g' -i filename 

Answer 2

• sed $'s/./&\\\n/g' (with BSD sed)
  • Or sed 's/./&\n/g' with GNU sed
  • Doesn't include empty lines for linefeeds
• fold -w1
  • -w specifies width in characters
  • Doesn't include empty lines for linefeeds
• while IFS= read -r -n1 -d '' c; do printf %s\\n "$c"; done
  • Includes empty lines for linefeeds with -d ''
  • The only option for read specified by POSIX is -r
• gawk -F '' 'OFS="\n"{$1=$1}1'
  • Or awk 'BEGIN{FS="";OFS="\n"}{$1=$1}1' in nawk (BSD awk, the awk that comes with OS X); it doesn't work with multibyte characters though
  • Neither includes empty lines for linefeeds

All except the nawk command worked with non-ASCII characters in my environment when LC_CTYPE was set to a UTF-8 locale. None collapsed or stripped spaces.