How to make ifstream follow symbolic link?

Question

In my C++ program I'm using ifstream("/etc/mtab", ios::ate|ios:in). An year back the program ran good but now ifstream::is_open() is returning false. By digging I found /etc/mtab is a symbolic link to /proc/mounts

--Update--

/proc/mounts is again a symbolic link to /proc/self/mounts which is actual file. I couldn't succeed opening this thought I'm running the program as a root user. So may be ifstream is following the symbolic link and is not able to open /proc/self/mounts

Can you `cat` (or `hexdump` or `md5sum` or whatever) the file? — 5gon12eder, Mar 07 '16 at 18:02
What error does it report? http://stackoverflow.com/a/17338934/1116364 — Daniel Jour, Mar 07 '16 at 18:05
But what error does it report? Please follow the link I provided! — Daniel Jour, Mar 07 '16 at 19:13
Can you post the output of running `stat` on all involved symlinks and files as well as a minimal code example that exhibits that behavior on your setup? Oh, and also check what `stream.good()` returns! Also check if you didnt accidentally move from the stream (did you switch to C++11) — Daniel Jour, Mar 07 '16 at 21:11

score 1 · Answer 1 · answered Apr 23 '20 at 09:25

although not directly answering on how to resolve symbolic links with std::fstream, a filesystem library was introduced by C++ 17 (was not available at the time this question was opened)

it can deal with symlinks by:

resolving symlinks: std::filesystem::read_symlink
copy symlinks: std::filesystem::copy_symlink
create symlinks: std::filesystem::create_symlink
test for symlink: std::filesystem::is_symlink

note that a filesystem library is also available in boost

How to make ifstream follow symbolic link?

1 Answers1