~ is expanded to current user home directory by shell, just like the variable $HOME.

While $HOME is expanded in most places (except inside single quotes), ~ is expanded only in a few specific conditions.

Here are a few examples where ~ is not expanded:

  • echo "~" '~'
  • echo ~@ ~~ (also note that ~u is meant to expand to the home directory of user u).
  • echo @~
  • (( HOME == ~ )), $(( var + ~ ))
  • with extglob: case $var in @(~|other))… (though case $var in ~|other) is OK).
  • ./configure --prefix=~ (as –prefix is not a valid variable name)
  • cmd "foo"=~ (in bash, because of the quotes).
  • when invoked as sh: export "foo"=~, env JAVA_HOME=~ cmd …

Especially for the ./configure --prefix=~ case, the following code doen’t work as intended.

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borg create --compression auto,zstd,10 --stats --list --filter=AME \
    --exclude "~/.config/mpv/watch_later" \
    ~/.config

The second ~ works, but the first one in --exclude doesn’t work. This has confused me for a long time.

Maybe it’s better to stick to $HOME.

References