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About bash : Tilde-in-path-doesnt-expand-to-home-directory

Question Detail

Say I have a folder called Foo located in /home/user/ (my /home/user also being represented by ~).

I want to have a variable

a="~/Foo" and then do

cd $a

I get
-bash: cd: ~/Foo: No such file or directory

However if I just do cd ~/Foo it works fine. Any clue on how to get this to work?

Question Answer

You can do (without quotes during variable assignment):

cd "$a"

But in this case the variable $a will not store ~/Foo but the expanded form /home/user/Foo. Or you could use eval:

eval cd "$a"

You can use $HOME instead of the tilde (the tilde is expanded by the shell to the contents of $HOME).

cd "$dir";

Although this question is merely asking for a workaround, this is listed as the duplicate of many questions that are asking why this happens, so I think it’s worth giving an explanation. According to https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06:

The order of word expansion shall be as follows:

Tilde expansion, parameter expansion, command substitution, and arithmetic expansion shall be performed, beginning to end.

When the shell evaluates the string cd $a, it first performs tilde expansion (which is a no-op, since $a does not contain a tilde), then it expands $a to the string ~/Foo, which is the string that is finally passed as the argument to cd.

A much more robust solution would be to use something like sed or even better, bash parameter expansion:

cd "${somedir/#\~/$HOME}"

or if you must use sed,

cd $(echo "$somedir" | sed "s#^~#$HOME#")

If you use double quotes the ~ will be kept as that character in $a.

cd $a will not expand the ~ since variable values are not expanded by the shell.

The solution is:

eval “cd $a”

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