NAME

creat − create a new file or rewrite an existing one

SYNOPSIS

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

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

DESCRIPTION

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

If the file exists, the length is truncated to 0 and the mode and owner are unchanged. 

If the file does not exist the file’s owner ID is set to the effective user ID of the process.  The group ID of the file is set to the effective group ID of the process, or if the S_ISGID bit is set in the parent directory then the group ID of the file is inherited from the parent directory.  The access permission bits of the file mode are set to the value of mode modified as follows:

If the group ID of the new file does not match the effective group ID or one of the supplementary group IDs, the S_ISGID bit is cleared. 

All bits set in the process’s file mode creation mask are cleared [see umask(2)]. 

The “save text image after execution bit” of the mode is cleared [see chmod(2) for the values of mode]. 

Upon successful completion, a write-only 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 the file.  The file descriptor is set to remain open across exec system calls [see fcntl(2)].  A new file may be created with a mode that forbids writing. 

The call creat(path, mode) is equivalent to:

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

creat fails if one or more of the following are true:

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

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

EACCES The file exists and write permission is denied. 

EAGAIN The file exists, mandatory file/record locking is set, and there are outstanding record locks on the file [see chmod(2)]. 

EFAULT path points outside the allocated address space of the process. 

EISDIR The named file is an existing directory. 

EINTR A signal was caught during the creat system call. 

ELOOP Too many symbolic links were encountered in translating path. 

EMFILE The process has too many open files [see getrlimit(2)]. 

ENAMETOOLONG The length of the path argument exceeds {PATH_MAX}, or the length of a path component exceeds {NAME_MAX} while _POSIX_NO_TRUNC is in effect. 

ENOTDIR A component of the path prefix is not a directory. 

ENOENT A component of the path prefix does not exist. 

ENOENT The path name is null. 

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. 

ENFILE The system file table is full. 

ENOLINK path points to a remote machine and the link to that machine is no longer active. 

EMULTIHOP Components of path require hopping to multiple remote machines. 

ENOSPC The file system is out of inodes. 

SEE ALSO

chmod(2), close(2), dup(2), fcntl(2), getrlimit(2), lseek(2), open(2), read(2), umask(2), write(2), stat(5)

DIAGNOSTICS

Upon successful completion a non-negative integer, namely the lowest numbered unused file descriptor, is returned.  Otherwise, a value of −1 is returned, no files are created or modified, and errno is set to indicate the error.