creat - create a new file or rewrite an existing one
int creat(const char *path, mode_t mode);
The creat() system call creates a new regular file or prepares to
rewrite an existing file named by the path name pointed to by path.
If the file exists, its length is truncated to 0, and its mode and
owner are unchanged. Otherwise, the file's owner ID is set to the
effective user ID of the process. If the set-group-ID bit of the
parent directory is set, the file's group ID is set to the group ID of
the parent directory. Otherwise, the file's group ID is set to the
process's effective group ID. The low-order 12 bits of the file mode
are set to the value of mode modified as follows:
+ 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)).
If the system call is made in 64 bit mode, the O_LARGEFILE status flag
is automatically set (see fcntl(5) or open(2)).
Upon successful completion, the file descriptor is returned and the
file is open for writing (only), even if the mode does not permit
writing. The file offset is set to the beginning of the file. The
file descriptor is set to remain open across exec*() system calls (see
fcntl(2)). Each process has a limit on how many files it can open
simultaneously. Refer to getrlimit(2) for the open files limit. This
is also discussed in open(2). A new file can be created with a mode
that forbids writing.
Access Control Lists - HFS File Systems Only
On HFS file systems that support access control lists, three base ACL
entries are created corresponding to the file access permission bits.
An existing file's access control list is unchanged by creat() (see
setacl(2), chmod(2), and acl(5)).
Access Control Lists - JFS File Systems Only
On JFS file systems that support access control lists, optional ACL
entries are created corresponding to the parent directory's default
ACL entries. An existing file's access control list is unchanged by
creat() (see acl(2), chmod(2), and aclv(5)).
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creat() returns the following values:
n Successful completion. n is the value of the file
descriptor. It is nonnegative.
-1 Failure. errno is set to indicate the error.
If creat() fails, errno is set to one of the following values.
[EACCES] Search permission is denied on a component of the
[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, enforcement mode file and record
locking is set and there are outstanding record
locks on the file.
[EDQUOT] User's disk quota block or inode limit has been
reached for this file system.
[EFAULT] path points outside the allocated address space of
the process. The reliable detection of this error
is implementation dependent.
[EISDIR] The named file is an existing directory.
[ELOOP] Too many symbolic links were encountered in
translating the path name.
[EMFILE] More than the maximum number of file descriptors
are currently open.
[ENAMETOOLONG] The length of the specified path name exceeds
PATH_MAX bytes, or the length of a component of
the path name exceeds NAME_MAX bytes while
_POSIX_NO_TRUNC is in effect.
[ENFILE] The system file table is full.
[ENOENT] The named file does not exist (for example, path
is null, or a component of path does not exist).
[ENOSPC] Not enough space on the file system.
[ENOTDIR] A component of the path prefix is not a directory.
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[ENXIO] The named file is a character special or block
special file, and the device associated with this
special file does not exist.
[EOVERFLOW] The named file is a regular file and the size of
the file cannot be represented correctly in an
object of type off_t.
[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.
chmod(2), close(2), creat64(2), dup(2), fcntl(2), lockf(2), lseek(2),
open(2), open64(2), read(2), setacl(2), truncate(2), umask(2),
write(2), acl(5), aclv(5).
creat(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1
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