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OPEN(2) System Calls Manual OPEN(2) NAME open, creat, close - open a file for reading or writing, create file SYNOPSIS int open(file, rwmode) char *file; int creat(file, mode) char *file; int close(fildes) DESCRIPTION Open opens the file, for reading if rwmode is 0, for writing if rwmode is 1, or for both if rwmode is 2, and returns an associated file de- scriptor. File is a null-terminated string representing a path name. The file pointer is set to 0. Creat creates a new file or prepares to rewrite an existing file, opens it for writing, and returns an associated file descriptor. If the file is new, the owner is set to the effective userid of the creating process; the group to that of the containing directory; the mode to mode as modified by the mode mask of the creating process; see umask(2). Mode need not allow writing. If the file already exists, it is truncated to 0 length; the mode, owner, and group remain unchanged, and must permit writing. A program may reserve a filename for exclusive use by calling creat with a mode that forbids writing. If the file does not exist, creat will succeed; further attempts to creat the same file will be denied. More sophisticated (but less portable) concurrent access control may be obtained by setting the S_ICCTYP field in the mode; see stat(2). Close closes the file associated with a file descriptor. Files are closed upon termination of a process, but since there is a limit on the number of open files per process, close is necessary for programs which deal with many files. It is possible to arrange for files to be closed by exec(2); see FIOCLEX in ioctl(2). SEE ALSO dup(2), pipe(2), read(2), exec(2), ioctl(2), stat(2), unlink(2) DIAGNOSTICS open, creat: EACCES, EBUSY, ECONC, EFAULT, EINTR, EIO, EISDIR, ELOOP, EMFILE, ENFILE, ENOENT, ENOTDIR, EROFS, ETXTBSY creat: ENOSPC close: EBADF BUGS It should be possible to call open without waiting for carrier on com- munication lines. The group of a newly-created file should (once again) be the effective groupid of the creating process. The trick of creating a file with an unwritable mode fails for the su- per-user. OPEN(2)