Hello world,

This is my first post on LQ. I have been banging my head on that one for an hour or two now ...

With bash, I noticed that you cannot do tilde expansion on input from the read builtin. That is very annoying. Compare:

[HTML]
#!/bin/bash

test=~/Desktop

if [ -d "$test" ]; then
echo "$test" # tilde expansion work, "/home/etienne/Desktop" is echoed
fi

read test2

if [ -d "$test2" ]; then
echo "$test2" # tilde expansion will not be done on test2
fi
[/HTML]

Tilde expansion in this context would be very helpful. For example, when writing an interactive script that is supposed to read directory names and act upon them.

Any way I can do tilde expansion on the result of the read builtin ? Or should I try another approach entirely ?

Many thanks in advance!

Try using the bash shell variable $HOME instead. e.g. $HOME/Desktop/...

That doesn't solve the problem either. The issue is that `read test` takes input from standard input literally without doing a shell scan and substitution of the input string. Once it is in a variable, you can't get recursive substitution. So, you never get the substitution in that original literal string that came in with `read test`.

However, you can request a shell processing of a string using the eval shell builtin command.

$ read test
$ eval test1=$test

will take the "~/Desktop" that is in test and end up with "/home/etienne/Desktop" in test1.

Right on, dude!

Thanks a lot. That's very clever, if somewhat unobvious. It would never have came to me.

great! i've been searching for this for 2 days, and now I found it.
thanks!

although, I found a potential problem with this: it is possible to inject bash commands
like this:

$ read test
~/directory;exit
$ eval something=$test

you can strip extra commands by using the bash specific syntax (probably easy to do it the /bin/sh compatible way, but I'm too lazy):
$ eval something=${test%%;*}