Question

我在Ubuntu上用C实现了共享内存概念。我创建了两个文件server.c和client.c，首先我编译了server.c然后编译了client.c并运行它。但它显示出错误。 “没有相应的文件和目录” 此错误出现在client.c文件中，因为找不到请求的共享内存段。请帮助我如何解决这个问题。

这是我的代码

server.c

  #include<sys/types.h>
  #include<sys/shm.h>
  #include<sys/ipc.h>
  #include<string.h>
  #include<stdlib.h>
  #include<stdio.h>
  #include<errno.h>

  #define SHMSIZE 100

 int main()
 {

 int shmid;
 key_t key;
 char *shm, *s;

 key=9876;
 shmid=shmget(key,SHMSIZE,IPC_CREAT|0666);
 if(shmid<0)
 {
 printf("%s",strerror(errno));
 perror("Error in Shared Memory get statement");
 exit(1);
 }

 shm=shmat(shmid,NULL,0);
 if(shm== (char *) -1)
 {
 perror("Error in Shared Memory attachment");
 exit(1);
 }

 memcpy(shm,"Hello World",11);
 s=shm;
 s+=11;

 while(*shm!='*')
 {
 sleep(1);
 }

 return 0;
 }

client.c

#include<sys/types.h>
#include<sys/shm.h>
#include<sys/ipc.h>
#include<string.h>
#include<stdlib.h>
#include<stdio.h>
#include<errno.h>

#define SHMSIZE 100

int main()
{

 int shmid;
 key_t key;
 char *shm, *s;

 key=9876;
 shmid=shmget(key,SHMSIZE,0666);
 if(shmid<0)
 {
 printf("%s",strerror(errno));
 perror("Error in Shared Memory get statement");
 exit(1);
 }

 shm=shmat(shmid,NULL,0);
 if(shm== (char *) -1)
 {
 printf("%s",strerror(errno));
 perror("Error in Shared Memory attachment");
 exit(1);
 }

 for(s=shm; *s!=0;s++)
 {
 printf("%c",*s);
 }
 printf("\n");
 *shm='*';
 return 0;
 }

Answer 1

shmget（）失败的事实是＆＃34;没有这样的文件或目录＆＃34;仅表示它没有找到带有该键的段（现在是迂腐的：不是id - 带有id我们通常引用shmget（）的值返回，随后使用） - 你检查了shmid是否相同？您的代码在我的系统上正常运行。

只是在它周围添加了一个main（）。希望它可以帮到你。

 key=9876;
 shmid=shmget(key,SHMSIZE,0666);
 if(shmid<0)
 {
        printf("%s",strerror(errno));
        perror("Error in Shared Memory get statement");
        shmid = shmget(key, SHMSIZE, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH | IPC_CREAT);
        if (shmid == -1)  {
                printf("%s",strerror(errno));
                perror("Error in Shared Memory get statement");
                exit(1);
        }
 }
printf("Shmget() successful %d\n",shmid);

Answer 2

我一直在调试 Frankenstein Linux 服务器，同时我从 php-7.4.22 opcache 复制了一些代码以获得相同的行为。

在我的情况下，此代码将 4 个 Segment 分配给 32MiB，总共 128MiB。

colormat = np.where(df1.eq(df2),
                    'background-color: green',
                    'background-color: red')

df1.style.apply(lambda _: colormat, axis=None)

运行它：/* +----------------------------------------------------------------------+ | Zend OPcache | +----------------------------------------------------------------------+ | Copyright (c) The PHP Group | +----------------------------------------------------------------------+ | This source file is subject to version 3.01 of the PHP license, | | that is bundled with this package in the file LICENSE, and is | | available through the world-wide-web at the following url: | | http://www.php.net/license/3_01.txt | | If you did not receive a copy of the PHP license and are unable to | | obtain it through the world-wide-web, please send a note to | | license@php.net so we can mail you a copy immediately. | +----------------------------------------------------------------------+ | Authors: Andi Gutmans <andi@php.net> | | Zeev Suraski <zeev@php.net> | | Stanislav Malyshev <stas@zend.com> | | Dmitry Stogov <dmitry@php.net> | +----------------------------------------------------------------------+ */ #include <sys/types.h> #include <sys/stat.h> #include <sys/shm.h> #include <sys/ipc.h> #include <string.h> #include <stdlib.h> #include <stdio.h> #include <errno.h> #ifndef MIN #define MIN(x, y) ((x) > (y) ? (y) : (x)) #endif #define REQUEST_SIZE 128 * 1024 * 1024; #define SEG_ALLOC_SIZE_MAX 32 * 1024 * 1024 #define SEG_ALLOC_SIZE_MIN 2 * 1024 * 1024 typedef struct { size_t size; size_t pos; /* position for simple stack allocator */ void *p; } zend_shared_segment; typedef struct { zend_shared_segment common; int shm_id; } zend_shared_segment_shm; int main() { key_t key = 9876; size_t requested_size = REQUEST_SIZE; int i; size_t allocate_size = 0, remaining_bytes = requested_size, seg_allocate_size; int first_segment_id = -1; key_t first_segment_key = -1; int shmget_flags; struct shmid_ds sds; zend_shared_segment_shm *shared_segments; zend_shared_segment_shm *shared_segments_p; int shared_segments_count = 0; printf("request_size: %d\n", requested_size); seg_allocate_size = SEG_ALLOC_SIZE_MAX; /* determine segment size we _really_ need: * no more than to include requested_size */ while (requested_size * 2 <= seg_allocate_size && seg_allocate_size > SEG_ALLOC_SIZE_MIN) { seg_allocate_size >>= 1; } shmget_flags = IPC_CREAT | SHM_R | SHM_W | IPC_EXCL; /* try allocating this much, if not - try shrinking */ while (seg_allocate_size >= SEG_ALLOC_SIZE_MIN) { allocate_size = MIN(requested_size, seg_allocate_size); first_segment_id = shmget(first_segment_key, allocate_size, shmget_flags); if (first_segment_id != -1) { break; } seg_allocate_size >>= 1; /* shrink the allocated block */ } printf("seg_allocate_size: %d\n", seg_allocate_size); if (first_segment_id == -1) { perror("Failed to allocate first segment"); return 1; } shared_segments_count = ((requested_size - 1) / seg_allocate_size) + 1; printf("shared_segments_count: %d\n", shared_segments_count); shared_segments_p = calloc(shared_segments_count, sizeof(zend_shared_segment_shm) + sizeof(void *) * (shared_segments_count)); if (!shared_segments_p) { perror("Failure in calloc"); return 1; } shared_segments = (zend_shared_segment_shm *)((char *)(shared_segments_p) + sizeof(void *) * (shared_segments_count)); remaining_bytes = requested_size; for (i = 0; i < shared_segments_count; i++) { allocate_size = MIN(remaining_bytes, seg_allocate_size); if (i != 0) { shared_segments[i].shm_id = shmget(IPC_PRIVATE, allocate_size, shmget_flags); } else { shared_segments[i].shm_id = first_segment_id; } if (shared_segments[i].shm_id == -1) { perror("Failed to allocate additional segments"); return 1; } shared_segments[i].common.p = shmat(shared_segments[i].shm_id, NULL, 0); if (shared_segments[i].common.p == (void *)-1) { perror("Failed to shmat"); shmctl(shared_segments[i].shm_id, IPC_RMID, &sds); return 1; } shmctl(shared_segments[i].shm_id, IPC_RMID, &sds); shared_segments[i].common.pos = 0; shared_segments[i].common.size = allocate_size; remaining_bytes -= allocate_size; } printf("Shmget() successful %d\n", first_segment_id); return 0; }

shmget中没有此类文件或目录错误

2 个答案: