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ftok()函数在不同平台下实现的兼容性
刚才试了一下,
RH9 下修改了 f 确实会影响 k,
再看 RH9 下对 ftok 的 man:
- FTOK(3) Linux Programmer's Manual FTOK(3)
- NAME
- ftok - convert a pathname and a project identifier to a System V IPC
- key
- SYNOPSIS
- # include <sys/types.h>;
- # include <sys/ipc.h>;
- key_t ftok(const char *pathname, int proj_id);
- DESCRIPTION
- The ftok function uses the identity of the file named by the given
- pathname (which must refer to an existing, accessible file) and the
- least significant 8 bits of proj_id (which must be nonzero) to generate
- a key_t type System V IPC key, suitable for use with msgget(2),
- semget(2), or shmget(2).
- The resulting value is the same for all pathnames that name the same
- file, when the same value of proj_id is used. The value returned should
- be different when the (simultaneously existing) files or the project
- IDs differ.
- RETURN VALUE
- On success the generated key_t value is returned. On failure -1 is
- returned, with errno indicating the error as for the stat(2) system
- call.
- CONFORMING TO
- XPG4
- NOTES
- Under libc4 and libc5 (and under SunOS 4.x) the prototype was
- key_t ftok(char *pathname, char proj_id);
- Today proj_id is an int, but still only 8 bits are used. Typical usage
- has an ASCII character proj_id, that is why the behaviour is said to be
- undefined when proj_id is zero.
- Of course no guarantee can be given that the resulting key_t is unique.
- Typically, a best effort attempt combines the given proj_id byte, the
- lower 16 bits of the i-node number, and the lower 8 bits of the device
- number into a 32-bit result. Collisions may easily happen, for example
- between files on /dev/hda1 and files on /dev/sda1.
- SEE ALSO
- ipc(5), msgget(2), semget(2), shmget(2), stat(2)
- Linux 2.4 2001-11-28 FTOK(3)
复制代码
按照我对 “ The resulting value is the same for all pathnames that name the same
file, ” 的理解,似乎不应该这样,
是不是可以认定是 RH9 的一个 BUG?? |
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