3.4 creat Function
A new file can also be created by
#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> int creat(const char
*pathname, mode_t mode); Returns: file descriptor
opened for write-only if OK,
-1 on error
Note that this function is equivalent to
open (pathname, O_WRONLY |
O_CREAT | O_TRUNC, mode);
In earlier versions of Unix the second argument to open could only be 0, 1, or 2. There was no way to open a file that didn't already exist. Therefore a separate system call, creat, was needed to create new files. With the O_CREAT and O_TRUNC options now provided by open, a separate creat function is no longer needed.
We'll show how to specify mode in Section 4.5 when we describe a file's access permissions in detail.
One deficiency with creat is that the file is opened only for writing. Before the new version of open was provided, if we were creating a temporary file that we wanted to write and then read back, we had to call creat, close, and then open. A better way is to use the new open function, as in
open (pathname, O_RDWR | O_CREAT | O_TRUNC, mode);