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System V的信号量是不支持名字,但是支持路径,但必须是一个确确实实存在的文件:- 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 non-zero) 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.
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