I have a variable in my bash script whose value is something like this:
~/a/b/c
Note that it is unexpanded tilde. When I do ls -lt on this variable (call it $VAR), I get no such directory. I want to let bash interpret/expand this variable without executing it. In other words, I want bash to run eval but not run the evaluated command. Is this possible in bash?
How did I manage to pass this into my script without expansion? I passed the argument in surrounding it with double quotes.
Try this command to see what I mean:
ls -lt "~"
This is exactly the situation I am in. I want the tilde to be expanded. In other words, what should I replace magic with to make these two commands identical:
ls -lt ~/abc/def/ghi
and
ls -lt $(magic "~/abc/def/ghi")
Note that ~/abc/def/ghi may or may not exist.
A safe way to use eval is
"$(printf "~/%q" "$dangerous_path")"
. Note that is bash specific.See this question for details
Also, note that under zsh this would be as as simple as
echo ${~dangerous_path}
How about this:
Or:
I believe this is what you're looking for
Example usage:
Just use
eval
correctly: with validation.Due to the nature of StackOverflow, I can't just make this answer unaccepted, but in the intervening 5 years since I posted this there have been far better answers than my admittedly rudimentary and pretty bad answer (I was young, don't kill me).
The other solutions in this thread are safer and better solutions. Preferably, I'd go with either of these two:
Original answer for historic purposes (but please don't use this)
If I'm not mistaken,
"~"
will not be expanded by a bash script in that manner because it is treated as a literal string"~"
. You can force expansion viaeval
like this.Alternatively, just use
${HOME}
if you want the user's home directory.Expanding (no pun intended) on birryree's and halloleo's answers: The general approach is to use
eval
, but it comes with some important caveats, namely spaces and output redirection (>
) in the variable. The following seems to work for me:Try it with each of the following arguments:
Explanation
${mypath//>}
strips out>
characters which could clobber a file during theeval
.eval echo ...
is what does the actual tilde expansion-e
argument are for support of filenames with spaces.Perhaps there's a more elegant solution, but this is what I was able to come up with.