creat(2)                                                 creat(2)



     NAME
          creat - create a new file or rewrite an existing one

     SYNOPSIS
          #include <sys/types.h>
          #include <sys/stat.h>
          #include <sys/fcntl.h>
          int creat(path, mode)
          char *path;
          mode mode;

     DESCRIPTION
          creat creates a new ordinary file or prepares to rewrite an
          existing file named by the pathname pointed to by path.

          If the file exists, the length is truncated to 0, and the
          mode and owner are unchanged.  Otherwise, the owner ID of
          the file is set to the effective user ID of the process, the
          group ID of the process is set to the effective group ID of
          the process, and the low-order 12 bits of the file mode are
          set to the value of mode modified as follows:

               All bits set in the file-mode-creation mask of the pro-
               cess are cleared.  See umask(2).

               Mode bit 01000 (save text image after execution bit) is
               cleared.  See chmod(2).

          For the POSIX environment the following constants for mode
          are defined in <sys/stat.h> :

          S_IRUSR        read permission, owner

          S_IWUSR        write permission, owner

          S_IXUSR        execute/search permission, owner

          S_IRGRP        read permission, group

          S_IWGRP        write permission, group

          S_IXGRP        execute/search permission, group

          S_IRUSR        read permission, others

          S_IWUSR        write permission, others

          S_IXUSR        execute/search permission, others

          On successful completion, the file descriptor is returned
          and the file is open for writing, even if the mode does not
          permit writing.  The file pointer is set to the beginning of



     April, 1990                                                     1

     creat(2)                                                 creat(2)



          the file.  The file descriptor is set to remain open across
          exec system calls, see fcntl(2).  No process may have more
          than the maximum number of files, OPEN_MAX, open simultane-
          ously.

          The mode given is arbitrary; it need not allow writing.
          This feature is used by programs that deal with temporary
          files of fixed names.  The creation is done with a mode that
          forbids writing.  Then if a second instance of the program
          attempts a creat, an error is returned, and the program
          knows that the name is unusable for the moment.

     RETURN VALUE
          On successful completion, a non-negative integer, namely the
          file descriptor, is returned.  Otherwise, a value of -1 is
          returned and errno is set to indicate the error.

     ERRORS
          creat will fail if one or more of the following are true:

          [ENOTDIR]    A component of the path prefix is not a direc-
                       tory.

          [ENAMETOOLONG]
                       A component of a pathname exceeded NAME_MAX
                       characters, or an entire pathname exceeded
                       PATH_MAX.

          [ELOOP]      Too many symbolic links were encountered in
                       translating a pathname.

          [ENOENT]     A component of the path prefix does not exist.

          [EACCES]     Search permission is denied on a component of
                       the path prefix.

          [ENOENT]     The pathname is null.

          [EACCES]     The file does not exist, and the directory in
                       which the file is to be created does not permit
                       writing.

          [EROFS]      The named file resides or would reside on a
                       read-only file system.

          [ETXTBSY]    The file is a pure-procedure (shared text) file
                       that is being executed.

                          Note:  If you are running a network file
                          system (NFS) and you are accessing a
                          shared binary remotely, it is possible
                          that you will not get this errno.



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     creat(2)                                                 creat(2)



          [EACCES]     The file exists, and write permission is
                       denied.

          [EISDIR]     The named file is an existing directory.

          [EMFILE]     The maximum number of file descriptors are
                       currently open.

          [EFAULT]     The path points outside the allocated address
                       space of the process.

          [ENFILE]     The system file table is full.

     BUGS
          The system-scheduling algorithm does not make this a true
          uninterruptible operation, and a race condition may develop
          if creat is done at precisely the same time by two different
          processes.

     SEE ALSO
          chmod(2), close(2), dup(2), fcntl(2), lseek(2), open(2),
          read(2), umask(2), write(2).

































     April, 1990                                                     3