制作一个列出目录中文件并对输出进行排序的程序

Question

我使用opendir(.)打开一个路径到我想从中读取的目录。然后我使用 readdir 循环遍历当前目录中的所有文件和目录。然后我有一个 char** 列表来存储 readdir 的内容。然后我对 **list 进行排序以按字典顺序排列。仅当我有一个长度超过 63 个字符的文件时，我才在对输出进行排序时不断收到溢出错误。为什么会这样，我该如何解决？

void ls_short() {
    char **list = NULL;
    int count = 0;
    DIR  *dir;
    struct dirent *rd;
    dir = opendir(".");
    // check to make sure that we can open the directory
    if(dir == NULL){
        perror("Not able to open The current directory.");
        exit(EXIT_FAILURE);
    }
    
    while((rd = readdir(dir)) != NULL){
        list = realloc(list, (count+1)*sizeof(*list));
        list[count] = rd ->d_name;
        ++count;
        printf("%s\n",rd ->d_name);
    }
    printf("here we will print the list\n");
    for (int i = 0; i < count;i++){
        printf("%s\n",list[i]);
    }
    printf("Now we print the list in order and also get rid of . and .. directory\n");
    list = realloc(list, (count+1)*sizeof(*list));
    list[count] = "";
    for (int i = 0; i < count - 1; i++){
        for (int j = 0; j < count - i - 1; j++){
            if (strcasecmp(list[j], list[j + 1]) > 0) {
                    char* temp;
                    temp = (char*)calloc(count, sizeof(char)*256);
                    strcpy(temp, list[j]);
                    strcpy(list[j], list[j + 1]);
                    strcpy(list[j + 1], temp);
                    free(temp);
            }
        }
    }
    for (int i = 2; i < count;i++){
        printf("%s\n",list[i]);
    }
    closedir(dir);
}

这是我收到的错误：

=================================================================
==43335==ERROR: AddressSanitizer: strcpy-param-overlap: memory ranges [0x6250000001fd,0x625000000220) and [0x62500000021d, 0x625000000240) overlap
    #0 0x103ef03ef in wrap_strcpy+0xaf (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x433ef)
    #1 0x103e9aa5d in ls_short ls.c:61
    #2 0x103e9a5c4 in main ls.c:16
    #3 0x7fff20379620 in start+0x0 (libdyld.dylib:x86_64+0x15620)

0x6250000001fd is located 253 bytes inside of 8192-byte region [0x625000000100,0x625000002100)
allocated by thread T0 here:
    #0 0x103ef54c0 in wrap_malloc+0xa0 (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x484c0)
    #1 0x7fff2025b0fe in _readdir_unlocked$INODE64+0x6d (libsystem_c.dylib:x86_64+0x2a0fe)
    #2 0x7fff2025b227 in readdir$INODE64+0x22 (libsystem_c.dylib:x86_64+0x2a227)
    #3 0x103e9a6ad in ls_short ls.c:42
    #4 0x103e9a5c4 in main ls.c:16
    #5 0x7fff20379620 in start+0x0 (libdyld.dylib:x86_64+0x15620)

0x62500000021d is located 285 bytes inside of 8192-byte region [0x625000000100,0x625000002100)
allocated by thread T0 here:
    #0 0x103ef54c0 in wrap_malloc+0xa0 (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x484c0)
    #1 0x7fff2025b0fe in _readdir_unlocked$INODE64+0x6d (libsystem_c.dylib:x86_64+0x2a0fe)
    #2 0x7fff2025b227 in readdir$INODE64+0x22 (libsystem_c.dylib:x86_64+0x2a227)
    #3 0x103e9a6ad in ls_short ls.c:42
    #4 0x103e9a5c4 in main ls.c:16
    #5 0x7fff20379620 in start+0x0 (libdyld.dylib:x86_64+0x15620)

SUMMARY: AddressSanitizer: strcpy-param-overlap (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x433ef) in wrap_strcpy+0xaf
==43335==ABORTING
Abort trap: 6

Answer 1

    while((rd = readdir(dir)) != NULL){
        list = realloc(list, (count+1)*sizeof(*list));
        list[count] = rd ->d_name;
        ++count;
        printf("%s\n",rd ->d_name);
    }

您没有在任何地方分配内存来保存要添加到列表中的字符串。您分配内存来保存指向它的指针，仅此而已。

您需要将 list[count] = rd ->d_name; 更改为：

    list[count] = malloc(256);
    strcpy(list[count], rd->d_name);

此外，排序时不需要为字符串分配新的内存。如果您已经为每个需要存储的字符串分配了内存（您必须这样做，否则您的列表已经损坏），为什么更改顺序需要分配新内存来保存字符串？

Answer 2

readdir() 有一个用于 rd->d_name 的静态缓冲区，它会在您每次调用它时重复使用，因此您所有的 list 元素都指向同一个字符串。

将字符串分配给数组时，您应该复制这些字符串。

list[count] = strdup(rd->d_name);

并且在排序时，不要在字符串之间复制名称，只需交换指针即可。

            if (strcasecmp(list[j], list[j + 1]) > 0) {
                char* temp;
                temp = list[j];
                list[j] = list[j+1];
                list[j+1] = temp;
            }

制作一个列出目录中文件并对输出进行排序的程序

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