sem_open problem Post: 7180

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Top Forums UNIX for Advanced & Expert Users sem_open problem Post 7180 by lance on Thursday 20th of September 2001 06:18:08 AM

09-20-2001

Registered User

sem_open problem

I can't compile these codes with g++.
my system is linux (kernel is 2.4.0 ).
When I try to compile this program with g++ -o semw semw.cpp
It always tells me that sem_open sem_close,sem_post do not exist.But I have checked semaphore.h,I can not find any problems.
Anyone can compile these codes in system linux ,and tell me the result ?May be it is the bug of linux ?

Code:

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <semaphore.h>
#include <fcntl.h>
#include <getopt.h>
#include <sys/types.h>
#include <sys/stat.h>

#define FILE_MODE S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH
int main(int argc,char **argv)
{
	int c,flags,fd;
	sem_t *sem;
	
	int val;
	if (argc!=2)
		fprintf(stderr,"usage:semwait<name>");
	
	fprintf(stderr,"usage:createSem [-e][-i initalvalue ]<name>");
	//sem=sem_open(argv[1],0);
	sem_open(argv[1],0);
	sem_post(sem);
	sem_wait(sem);
	
	pause();
	exit(0);
}

added code tags for readability --oombera

Last edited by oombera; 02-20-2004 at 11:33 AM..

lance

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LEARN ABOUT FREEBSD

sem_post

SEM_POST(3)						   BSD Library Functions Manual 					       SEM_POST(3)

NAME

     sem_post -- increment (unlock) a semaphore

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <semaphore.h>

     int
     sem_post(sem_t *sem);

DESCRIPTION

     The sem_post() function increments (unlocks) the semaphore pointed to by sem.  If there are threads blocked on the semaphore when sem_post()
     is called, then the highest priority thread that has been blocked the longest on the semaphore will be allowed to return from sem_wait().

     The sem_post() function is signal-reentrant and may be called within signal handlers.

RETURN VALUES

     The sem_post() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
     cate the error.

ERRORS

     The sem_post() function will fail if:

     [EINVAL]		The sem argument points to an invalid semaphore.

     [EOVERFLOW]	The semaphore value would exceed SEM_VALUE_MAX.

SEE ALSO

     sem_getvalue(3), sem_trywait(3), sem_wait(3)

STANDARDS

     The sem_post() function conforms to ISO/IEC 9945-1:1996 (``POSIX.1'').

BSD
								 January 28, 2015							       BSD

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