Opening a file on unix using c++

Question

I am trying to open a file in c++ and the server the progam in running on is based on tux.

string filename = "../dir/input.txt"; works but
string filename = "~jal/dir1/dir/input.txt"; fails

Is there any way to open a file in c++ when the filename provided is in the second format?

Answer 1

The ~jal expansion is performed by the shell (bash/csh/whatever), not by the system itself, so your program is trying to look into the folder named ~jal/, not /home/jal/.

I'm not a C coder, but getpwent() may be what you need.

Answer 2

You could scan the string, replacing ~user by the appropriate directory.

The POSIX function wordexp does that, and a few other things

• variable substitution, like you can use $HOME
• optional command substitution, like $(echo foo) (can be disabled)
• arithmetic expansion, like $((3+4))
• word splitting, like splitting ~/a ~/b into two words
• wildcard expansion, like *.cpp
• and quoting, like "~/a ~/b" remains that

Answer 3

Here is a ready piece of code, that performs this task:

How do I expand `~' in a filename like the shell does?