Hi
Expansion of the tilde symbol does not happen in several cases, it can be a pain.
I have had to put in specific paths in just the same situation as you.
As well as the case you mentioned, using a string like "~/test.txt" to write a file can sometimes create a directory '~' in the current working directory, with the file test.txt inside it, not what was intended!
EDIT: (didn't explain why)
The crux of the problem is that the tilde expansion is something bash does, so does not work outside of that environment.
C libraries have no idea what it is, so system("echo 123456789 > ~/myhome.txt"); will probably work whereas fptr = fopen("~/myhome.txt", w); fwrite(fptr,"123456789"); will not.
To reliably get the home directory of the current user in C programs, you need to get the password struct and get homedir from that
#include <pwd.h>
struct passwd *pw = getpwuid(getuid());
const char *homedir = pw->pw_dir;
The environment variable HOME is generally available and in a lot of cases (certainly in scripts) the string
$HOME/linuxcnc/ncfiles will work instead of
~/linuxcnc/ncfiles for example
Try
echo $HOME in a terminal and it should show your home dir
regards
