creat(), creat64()

Create and open a file (low-level)

Synopsis:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int creat( const char* path, 
           mode_t mode );

int creat64( const char* path, 
             mode_t mode );

Arguments:

path

The path of the file you want to open.

mode

The access permissions that you want to use. For more information, see “Access permissions” in the documentation for stat().

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The creat() and creat64() functions create and open the file specified by path with the given mode.

Calling creat() is the same as:

open( path, O_WRONLY | O_CREAT | O_TRUNC, mode );

Similarly, calling creat64() is the same as:

open64( path, O_WRONLY | O_CREAT | O_TRUNC | O_LARGEFILE, mode );

If path exists and is writable, it's truncated to contain no data, and the existing mode setting isn't changed.

If path doesn't exist, it's created with the access permissions specified by the mode argument. The access permissions for the file or directory are specified as a combination of the bits defined in <sys/stat.h>.

Returns:

A file descriptor on success, or -1 if an error occurs (errno is set).

Errors:

EACCES

Indicates one of the following permission problems:

• Search permission is denied for one of the components in the path.
• The file specified by path exists, and the permissions specified by mode are denied.
• The file specified by path doesn't exist, and the file couldn't be created because write permission is denied for the parent directory.

EBADFSYS

While attempting to open path, the file itself or a component of its path prefix was found to be corrupted. A system failure — from which no automatic recovery is possible — occurred while the file was being written to or while the directory was being updated. The filesystem must be repaired before proceeding.

EBUSY

The file specified by path is a block special device that's already open for writing, or path names a file on a filesystem mounted on a block special device that is already open for writing.

EINTR

The call to creat() was interrupted by a signal.

EISDIR

The file specified by path is a directory and the file creation flags specify write-only or read/write access.

ELOOP

Too many levels of symbolic links.

EMFILE

This process is using too many file descriptors.

ENAMETOOLONG

The length of path exceeds PATH_MAX, or a pathname component is longer than NAME_MAX.

ENFILE

Too many files are currently open in the system.

ENOENT

Either the path prefix doesn't exist, or the path argument points to an empty string.

ENOSPC

The directory or filesystem that would contain the new file doesn't have enough space available to create a new file.

ENOSYS

The creat() function isn't implemented for the filesystem specified by path.

ENOTDIR

A component of the path prefix isn't a directory.

EROFS

The file specified by path resides on a read-only filesystem.

Examples:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

int main( void )
{
    int filedes;

    filedes = creat( "file",
                 S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP );
    if( filedes != -1 ) {
        /* process file */

        close( filedes );

        return EXIT_SUCCESS;
    }

    return EXIT_FAILURE;
}

Classification:

creat() is POSIX 1003.1; creat64() is Large-file support

See also:

chsize(), close(), dup(), dup2(), eof(), errno, execl(), execle(), execlp(), execlpe(), execv(), execve(), execvp(), execvpe(), fcntl(), fileno(), fstat(), isatty(), lseek(), open(), read(), sopen(), stat(), tell(), write(), umask()