Open file in linux. I don't want to create a write-protected file

Question

I have a problem when I create a file in Linux it makes my file write-protected and I don't know why it does that.

void fileOperation::openFileWrite(char x, off_t s)
{
  int fd;
  char c[2] = {x};

  fd = open("/home/stud/txtFile", O_CREAT | O_WRONLY);  //open file
  if(fd == -1)
      cout << "can't open file" << endl;
  else
  {
      lseek(fd, s, SEEK_SET);//seek at first byte
      write(fd, (void*)&c, 2);//write to file
  }
  syncfs(fd);
  ::close(fd);
}

You should use `perror` on failure... – Basile Starynkevitch Oct 24 '14 at 11:00 — Basile Starynkevitch, Oct 24 '14 at 11:00

score 5 · Accepted Answer · answered Oct 24 '14 at 08:41

5

You have to use additional argument with write permission set (default permission for you may be taking write permission off)

 fd = open("/home/stud/txtFile", O_CREAT | O_WRONLY, 0666);//open file

0666 is an octal number, i.e. every one of the 6's corresponds to three permission bits

6 = rw
7 = rwx

answered Oct 24 '14 at 08:41

Dr. Debasish Jana

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Thank you very much it sovled the problem. – Loc Dai Le Oct 24 '14 at 08:48
You have to tag their name with the `@` symbol to get their attention like: @LocDaiLe – Galik Oct 24 '14 at 10:05
@LocDaiLe if the answer fixed your problem, be sure to mark it as correct (click the green checknext to the answer) – Jonesopolis Aug 19 '15 at 14:06

score 1 · Answer 2 · answered Oct 24 '14 at 08:38

1

You probably have a restrictive umask. The open call will simply attempt to create a file with mode 0666 but the user's umask typically removes many of those permission bits.

answered Oct 24 '14 at 08:38

tripleee

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Open file in linux. I don't want to create a write-protected file

2 Answers2