It's a single binary, cross-OS, cross-arch.

Go to https://cosmo.zip/pub/cosmos/bin/ and download an executable, like https://cosmo.zip/pub/cosmos/bin/basename .

  % curl -O https://cosmo.zip/pub/cosmos/bin/basename
    % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  100  663k  100  663k    0     0   440k      0  0:00:01  0:00:01 --:--:--  441k
  % chmod +x basename

On macOS with an M1:

  % arch
  arm64
  % sha256sum basename
  2e4cf8378b679dd0c2cdcc043bb1f21eaf464d3c3b636ed101fbc5e3230eb5fb  basename
  % file ./basename
  ./basename: DOS/MBR boot sector; partition 1 : ID=0x7f, active, start-CHS (0x0,0,1), end-CHS (0x3ff,255,63), startsector 0, 4294967295 sectors
  % ./basename /dev/null.txt
  null.txt

On FreeBSD with an amd64:

  % uname -sm
  FreeBSD amd64
  % sha256sum basename
  2e4cf8378b679dd0c2cdcc043bb1f21eaf464d3c3b636ed101fbc5e3230eb5fb  basename
  % file basename
  basename: DOS/MBR boot sector; partition 1 : ID=0x7f, active, start-CHS (0x0,0,1), end-CHS (0x3ff,255,63), startsector 0, 4294967295 sectors
  % ./basename /dev/null.pdf
  null.pdf

Kind of. It can be read as a single binary, some supported systems will do that. In others, the executable is first parsed as a shell script. There's definitely more to it than a single binary.

    MZqFpD='

     ø       
 @               ' <<'justine0e5c7z'
    È 
 ²@ë 됐ëHƒì1Ò½  ëéE  ü‡>à¿ p1ÉŽÁúŽ×‰Ìûè  ^îr ¸ PP 1ÿ¹ ó¤‡ÒÿêŽ   ŽÙ¹ ¸P ŽÀ1À1ÿóª€ú@tè  °
1É0ö¿Pèo ŒÆƒÆ ŽÆOuóê '  SR´Ís1ÀÍrF¸
¹
 ¶ » ŽÃ1ÛÍr3´Ír-ˆÏ€ç?€áÀÐÁÐÁ†Í1öŽÆ¾‡÷¥¥¥¥¥¤“«®‘«’«Xª’[ÃZ€ò€1ÀÍr÷ë¡PQ†ÍÐÉÐÉÁ1Û°
´ÍYXrþÀ:$v
    °
þÆ:6)v0öAÃP1ÀÍXë̉þ¬„Àt »  ´ÍëòÃW¿¹&èèÿ_èäÿ¿Á&èÞÿóëü¹ ¾ ­…Àt
    QV—¾Ð&è ^YâîÉú…ÒtRV1ɱ
ʬ^ €îZ¬îBIyúà              € 
 ÿÿÿ    ÿÿÿÿ                                                Uª
    justine0e5c7z
    #'"

    o=$(command -v "$0")
    [ x"$1" != x--assimilate ] && type ape >/dev/null 2>&1 && exec ape "$o" "$@"
    t="${TMPDIR:-${HOME:-.}}/.ape-1.10"
    [ x"$1" != x--assimilate ] && [ -x "$t" ] && exec "$t" "$o" "$@"
    m=$(uname -m 2>/dev/null) || m=x86_64
    if [ ! -d /Applications ]; then
    if [ x"$1" = x--assimilate ]; then
    if [ "$m" = x86_64 ] || [ "$m" = amd64 ]; then
    exec 7<> "$o" || exit 121
    printf '\177ELF\2\1\1\11\0\0\0\0\0\0\0\0\2\0>\0\1\0\0\0vE@\0\0\0\0\0\510\013\000\000\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\100\0\70\0\006\000\0\0\0\0\0\0' >&7
    exec 7<&-
    fi
    exit

Reminds me of a cool tool I once used, uudecode.com, which was a DOS binary that only used 7-bit characters and could decode uuencoded (base64 predecessor) files. Was useful for getting attachments through e-mail in the face of all kinds of filters.

https://news.ycombinator.com/item?id=16312317 - "A C89 compiler that produces executables that are also valid ASCII text files"

http://tom7.org/abc/

The paper for SIGBOVIK 2017 is both a text file and an executable.

Really near.

Also discussed 11 months ago:

https://news.ycombinator.com/item?id=36821985 (15 comments)