creat(2)                                                 creat(2)



NAME
     creat - creates a new file or rewrites an existing one

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

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

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

     If the file exists, the length is truncated to 0, and the
     mode and owner are unchanged.  Otherwise, the owner ID of
     the file is set to the effective user ID of the process, the
     group ID of the process is set to the effective group ID of
     the process, and the low-order 12 bits of the file mode are
     set to the value of mode, modified as follows:

     ⊕    All bits set in the file-mode-creation mask of the
          process are cleared.  See umask(2).

     ⊕    Mode bit 01000 (save-text-image-after-execution bit) is
          cleared.  See chmod(2).

     For the POSIX environment, the following constants for mode
     are defined in <sys/stat.h>:

          S_IRUSR
               read permission, owner

          S_IWUSR
               write permission, owner

          S_IXUSR
               execute/search permission, owner

          S_IRGRP
               read permission, group

          S_IWGRP
               write permission, group

          S_IXGRP
               execute/search permission, group

          S_IROTH
               read permission, others



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creat(2)                                                 creat(2)



          S_IWOTH
               write permission, others

          S_IXOTH
               execute/search permission, others

     On successful completion, the 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)).  No process can have more
     than the maximum number of files, OPEN_MAX, open
     simultaneously.

     mode is arbitrary; it need not allow writing.  This feature
     is used by programs that deal with temporary files of fixed
     names.  The creation is done with a mode that forbids
     writing.  Then, if a second instance of the program attempts
     a creat operation, an error is returned, and the program
     knows that the name is unusable for the moment.

STATUS MESSAGES AND VALUES
     On successful completion, a nonnegative integer, namely the
     file descriptor, is returned.  Otherwise, a value of -1 is
     returned and errno is set to indicate the error.

     The creat command will fail if one or more of the following
     conditions is true:

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

     ENAMETOOLONG
          A component of a pathname exceeded NAME_MAX characters,
          or an entire pathname exceeded PATH_MAX.

     ELOOP
          Too many symbolic links were encountered in translating
          a pathname.

     ENOENT
          A component of the path prefix does not exist.

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

     ENOENT
          The pathname is null.

     EACCES
          The file does not exist, and the directory in which the



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creat(2)                                                 creat(2)



          file is to be created does not permit writing.

     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.

             Note:  If you are running the Network File System
             (NFS) and you are accessing a shared binary
             remotely, it is possible that you will not get
             this errno result.


     EACCES
          The file exists, and write permission is denied.

     EISDIR
          The named file is an existing directory.

     EMFILE
          The maximum number of file descriptors is currently
          open.

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

     ENFILE
          The system-file table is full.

LIMITATIONS
     The system-scheduling algorithm does not make creat a true
     uninterruptible operation, and a race condition may develop
     if creat is executed at precisely the same time by two
     different processes.

SEE ALSO
     chmod(2), close(2), dup(2), fcntl(2), lseek(2), open(2),
     read(2), umask(2), write(2)













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