On my Linux Mint 19.1:
```bash
$ umask
0022
```

After the first run of `bitcoin-qt -sysperm=false` the `0700` permissions are expected for both the datadir (`~/.bitcoin`) and the walletdir (`~/.bitcoin/wallets`).

Actually, the directories are created with such access permissions:
```bash
$ stat ~/.bitcoin | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
$ stat ~/.bitcoin/wallets | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
```

Refs:
- #4286
- #13371
- #13389

NOTE: reading through the initial PR #4286 makes me think it was controversial. Is it a better and simpler way to just get rid of `-sysperm` option? I believe a user who needs this option can easily run `chown` command.
{
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#endif
}
bool TruncateFile(FILE *file, unsigned int length) {
#if defined(WIN32)
    return _chsize(_fileno(file), length) == 0;
#else
    return ftruncate(fileno(file), length) == 0;
#endif
}
/**
 * this function tries to raise the file descriptor limit to the requested number.
 * It returns the actual file descriptor limit (which may be more or less than nMinFD)
 */
int RaiseFileDescriptorLimit(int nMinFD) {