| /**************************************************************************** |
| | (C) Copyright 2008 Novell, Inc. All Rights Reserved. |
| | |
| | GPLv2: This program is free software; you can redistribute it |
| | and/or modify it under the terms of version 2 of the GNU General |
| | Public License as published by the Free Software Foundation. |
| | |
| | This program is distributed in the hope that it will be useful, |
| | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| | GNU General Public License for more details. |
| +-------------------------------------------------------------------------*/ |
| |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| #include <fcntl.h> |
| #include <unistd.h> |
| #include <stdlib.h> |
| #include <stdio.h> |
| |
| #include <puny.h> |
| |
| /* |
| * NAME |
| * open, creat - open and possibly create a file or device |
| * |
| * SYNOPSIS |
| * #include <sys/types.h> |
| * #include <sys/stat.h> |
| * #include <fcntl.h> |
| * |
| * int open(const char *pathname, int flags); |
| * int open(const char *pathname, int flags, mode_t mode); |
| * int creat(const char *pathname, mode_t mode); |
| * |
| * DESCRIPTION |
| * The open() system call is used to convert a pathname into a file |
| * descriptor (a small, non-negative integer for use in subsequent I/O as |
| * with read, write, etc.). When the call is successful, the file descrip- |
| * tor returned will be the lowest file descriptor not currently open for |
| * the process. This call creates a new open file, not shared with any |
| * other process. (But shared open files may arise via the fork(2) system |
| * call.) The new file descriptor is set to remain open across exec func- |
| * tions (see fcntl(2)). The file offset is set to the beginning of the |
| * file. |
| * |
| * The parameter flags is one of O_RDONLY, O_WRONLY or O_RDWR which request |
| * opening the file read-only, write-only or read/write, respectively, bit- |
| * wise-or'd with zero or more of the following: |
| * |
| * O_CREAT |
| * If the file does not exist it will be created. The owner (user |
| * ID) of the file is set to the effective user ID of the process. |
| * The group ownership (group ID) is set either to the effective |
| * group ID of the process or to the group ID of the parent direc- |
| * tory (depending on filesystem type and mount options, and the |
| * mode of the parent directory, see, e.g., the mount options bsd- |
| * groups and sysvgroups of the ext2 filesystem, as described in |
| * mount(8)). |
| * |
| * O_EXCL When used with O_CREAT, if the file already exists it is an error |
| * and the open will fail. In this context, a symbolic link exists, |
| * regardless of where its points to. O_EXCL is broken on NFS file |
| * systems, programs which rely on it for performing locking tasks |
| * will contain a race condition. The solution for performing |
| * atomic file locking using a lockfile is to create a unique file |
| * on the same fs (e.g., incorporating hostname and pid), use |
| * link(2) to make a link to the lockfile. If link() returns 0, the |
| * lock is successful. Otherwise, use stat(2) on the unique file to |
| * check if its link count has increased to 2, in which case the |
| * lock is also successful. |
| * |
| * O_NOCTTY |
| * If pathname refers to a terminal device -- see tty(4) -- it will |
| * not become the process's controlling terminal even if the process |
| * does not have one. |
| * |
| * O_TRUNC |
| * If the file already exists and is a regular file and the open |
| * mode allows writing (i.e., is O_RDWR or O_WRONLY) it will be |
| * truncated to length 0. If the file is a FIFO or terminal device |
| * file, the O_TRUNC flag is ignored. Otherwise the effect of |
| * O_TRUNC is unspecified. (On many Linux versions it will be |
| * ignored; on other versions it will return an error.) |
| * |
| * O_APPEND |
| * The file is opened in append mode. Before each write, the file |
| * pointer is positioned at the end of the file, as if with lseek. |
| * O_APPEND may lead to corrupted files on NFS file systems if more |
| * than one process appends data to a file at once. This is because |
| * NFS does not support appending to a file, so the client kernel |
| * has to simulate it, which can't be done without a race condition. |
| * |
| * O_NONBLOCK or O_NDELAY |
| * When possible, the file is opened in non-blocking mode. Neither |
| * the open nor any subsequent operations on the file descriptor |
| * which is returned will cause the calling process to wait. For |
| * the handling of FIFOs (named pipes), see also fifo(4). This mode |
| * need not have any effect on files other than FIFOs. |
| * |
| * O_SYNC The file is opened for synchronous I/O. Any writes on the result- |
| * ing file descriptor will block the calling process until the data |
| * has been physically written to the underlying hardware. See |
| * RESTRICTIONS below, though. |
| * |
| * O_NOFOLLOW |
| * If pathname is a symbolic link, then the open fails. This is a |
| * FreeBSD extension, which was added to Linux in version 2.1.126. |
| * Symbolic links in earlier components of the pathname will still |
| * be followed. The headers from glibc 2.0.100 and later include a |
| * definition of this flag; kernels before 2.1.126 will ignore it if |
| * used. |
| * |
| * O_DIRECTORY |
| * If pathname is not a directory, cause the open to fail. This |
| * flag is Linux-specific, and was added in kernel version 2.1.126, |
| * to avoid denial-of-service problems if opendir(3) is called on a |
| * FIFO or tape device, but should not be used outside of the imple- |
| * mentation of opendir. |
| * |
| * O_LARGEFILE |
| * On 32-bit systems that support the Large Files System, allow |
| * files whose sizes cannot be represented in 31 bits to be opened. |
| * |
| * Some of these optional flags can be altered using fcntl after the file |
| * has been opened. |
| * |
| * The argument mode specifies the permissions to use in case a new file is |
| * created. It is modified by the process's umask in the usual way: the |
| * permissions of the created file are (mode & ~umask). Note that this |
| * mode only applies to future accesses of the newly created file; the open |
| * call that creates a read-only file may well return a read/write file |
| * descriptor. |
| * |
| * The following symbolic constants are provided for mode: |
| * |
| * S_IRWXU |
| * 00700 user (file owner) has read, write and execute permission |
| * |
| * S_IRUSR (S_IREAD) |
| * 00400 user has read permission |
| * |
| * S_IWUSR (S_IWRITE) |
| * 00200 user has write permission |
| * |
| * S_IXUSR (S_IEXEC) |
| * 00100 user has execute permission |
| * |
| * S_IRWXG |
| * 00070 group has read, write and execute permission |
| * |
| * S_IRGRP |
| * 00040 group has read permission |
| * |
| * S_IWGRP |
| * 00020 group has write permission |
| * |
| * S_IXGRP |
| * 00010 group has execute permission |
| * |
| * S_IRWXO |
| * 00007 others have read, write and execute permission |
| * |
| * S_IROTH |
| * 00004 others have read permission |
| * |
| * S_IWOTH |
| * 00002 others have write permisson |
| * |
| * S_IXOTH |
| * 00001 others have execute permission |
| * |
| * mode should always be specified when O_CREAT is in the flags, and is |
| * ignored otherwise. |
| * |
| * creat is equivalent to open with flags equal to |
| * O_CREAT|O_WRONLY|O_TRUNC. |
| * |
| * RETURN VALUE |
| * open and creat return the new file descriptor, or -1 if an error |
| * occurred (in which case, errno is set appropriately). Note that open |
| * can open device special files, but creat cannot create them - use |
| * mknod(2) instead. |
| * |
| * On NFS file systems with UID mapping enabled, open may return a file |
| * descriptor but e.g. read(2) requests are denied with EACCES. This is |
| * because the client performs open by checking the permissions, but UID |
| * mapping is performed by the server upon read and write requests. |
| * |
| * If the file is newly created, its atime, ctime, mtime fields are set to |
| * the current time, and so are the ctime and mtime fields of the parent |
| * directory. Otherwise, if the file is modified because of the O_TRUNC |
| * flag, its ctime and mtime fields are set to the current time. |
| * |
| * ERRORS |
| * EEXIST pathname already exists and O_CREAT and O_EXCL were used. |
| * |
| * EISDIR pathname refers to a directory and the access requested involved |
| * writing. |
| * |
| * EACCES The requested access to the file is not allowed, or one of the |
| * directories in pathname did not allow search (execute) permis- |
| * sion, or the file did not exist yet and write access to the par- |
| * ent directory is not allowed. |
| * |
| * ENAMETOOLONG |
| * pathname was too long. |
| * |
| * ENOENT A directory component in pathname does not exist or is a dangling |
| * symbolic link. |
| * |
| * ENOTDIR |
| * A component used as a directory in pathname is not, in fact, a |
| * directory, or O_DIRECTORY was specified and pathname was not a |
| * directory. |
| * |
| * ENXIO O_NONBLOCK | O_WRONLY is set, the named file is a FIFO and no |
| * process has the file open for reading. Or, the file is a device |
| * special file and no corresponding device exists. |
| * |
| * ENODEV pathname refers to a device special file and no corresponding |
| * device exists. (This is a Linux kernel bug - in this situation |
| * ENXIO must be returned.) |
| * |
| * EROFS pathname refers to a file on a read-only filesystem and write |
| * directory, or O_DIRECTORY was specified and pathname was not a |
| * directory. |
| * |
| * ENXIO O_NONBLOCK | O_WRONLY is set, the named file is a FIFO and no |
| * process has the file open for reading. Or, the file is a device |
| * special file and no corresponding device exists. |
| * |
| * ENODEV pathname refers to a device special file and no corresponding |
| * device exists. (This is a Linux kernel bug - in this situation |
| * ENXIO must be returned.) |
| * |
| * EROFS pathname refers to a file on a read-only filesystem and write |
| * access was requested. |
| * |
| * ETXTBSY |
| * pathname refers to an executable image which is currently being |
| * executed and write access was requested. |
| * |
| * EFAULT pathname points outside your accessible address space. |
| * |
| * ELOOP Too many symbolic links were encountered in resolving pathname, |
| * or O_NOFOLLOW was specified but pathname was a symbolic link. |
| * |
| * ENOSPC pathname was to be created but the device containing pathname has |
| * no room for the new file. |
| * |
| * ENOMEM Insufficient kernel memory was available. |
| * |
| * EMFILE The process already has the maximum number of files open. |
| * |
| * ENFILE The limit on the total number of files open on the system has |
| * been reached. |
| * |
| * CONFORMING TO |
| * SVr4, SVID, POSIX, X/OPEN, BSD 4.3 The O_NOFOLLOW and O_DIRECTORY flags |
| * are Linux-specific. One may have to define the _GNU_SOURCE macro to get |
| * their definitions. |
| * |
| * RESTRICTIONS |
| * There are many infelicities in the protocol underlying NFS, affecting |
| * amongst others O_SYNC and O_NDELAY. |
| * |
| * POSIX provides for three different variants of synchronised I/O, corre- |
| * sponding to the flags O_SYNC, O_DSYNC and O_RSYNC. Currently (2.1.130) |
| * these are all synonymous under Linux. |
| * |
| * SEE ALSO |
| * read(2), write(2), fcntl(2), close(2), link(2), mknod(2), mount(2), |
| * stat(2), umask(2), unlink(2), socket(2), fopen(3), fifo(4) |
| * |
| * Linux 1999-06-03 OPEN(2) |
| */ |
| |
| int main (int argc, char *argv[]) |
| { |
| int fd; |
| |
| punyopt(argc, argv, NULL, NULL); |
| fd = creat(Option.file, 0666); |
| if (fd == -1) { |
| perror(Option.file); |
| exit(1); |
| } |
| close(fd); |
| return 0; |
| } |
