creat - Create New File

Syntax

#include <io.h>
#include <sys\stat.h>
int creat(char *pathname, int pmode);

Description
creat either creates a new file or opens and truncates an existing file. If the file specified by pathname does not exist, creat creates a new file with the given permission setting and opens it for writing in text mode. If the file already exists, and the read-only attribute and sharing permissions allow writing, creat truncates the file to length 0. This action destroys the previous contents of the file and opens it for writing in text mode. creat always opens a file in text mode for reading and writing.

The permission setting pmode applies to newly created files only. The new file receives the specified permission setting after you close it for the first time. The pmode integer expression contains one or both of the constants S_IWRITE and S_IREAD, defined in <sys\stat.h>. The values of the pmode argument and their meanings are: compact break=fit.

Value

Meaning
S_IREAD
Reading permitted
S_IWRITE
Writing permitted
S_IREAD | S_IWRITE
Reading and writing permitted.

If you do not give permission to write to the file, it is a read-only file. On the OS/2 operating system, you cannot give write-only permission. Thus, the modes S_IWRITE and S_IREAD | S_IWRITE have the same results. The creat function applies the current file permission mask to pmode before setting the permissions. (See umask for more information about file permission masks.)

When writing new code, you should use open rather than creat.

Specifying a pmode of S_IREAD is similar to making a file read-only with the ATTRIB system command.

Returns

creat returns a handle for the created file if the call is successful. A return value of -1 shows an error, and creat sets errno to one of the following values:

Value

Meaning
EACCESS
File sharing violated.
EINVAL
The mode specified was not valid.
EMFILE
No more file handles are available.
ENOENT
The path name was not found, or the file name was incorrect.
EOS2ERR
The call to the operating system was not successful.
Example Code

This example creates the file sample.dat so it can be read from and written to.

#include <sys\stat.h>#include <io.h>
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
   int fh;

   fh = creat("sample.dat", S_IREAD|S_IWRITE);
   if (-1 == fh) {
      perror("Error in creating sample.dat");
      return EXIT_FAILURE;
   }
   else
      printf("Successfully created sample.dat.\n");
   close(fh);
   return 0;

   /****************************************************************************
      The output should:

       Successfully created sample.dat.
   ****************************************************************************/
}

Related Information

• chmod
  
• close
  
• open
  
• fdopen
  
• sopen
  
• umask

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