netdata：readlink获取文件描述符对应的文件名

迈不过友情╰ 2023-01-02 05:25 416阅读 0赞

#include <stdio.h>
    #include <fcntl.h>
    #include <stdlib.h>
    #include <zconf.h>
    
    
    typedef struct procfile {
        
        char filename[FILENAME_MAX + 1];
        int fd;
    } procfile;
    
    #define PROCFILE_INCREMENT_BUFFER 512
    procfile *procfile_open(const char *filename) {
        
        int fd = open(filename, O_RDONLY, 0666);
        if(fd == -1) {
        
            printf("(%s)%d: Cannot open file '%s'",  __FUNCTION__ , __LINE__, filename);
            return NULL;
        }
    
        procfile *ff = malloc(sizeof(procfile) + PROCFILE_INCREMENT_BUFFER);
        ff->filename[0] = '\0';
        ff->fd = fd;
    
    
        return ff;
    }
    
    char *procfile_filename(procfile *ff) {
        
        if(ff->filename[0]) return ff->filename;  // filename != 00000000
    
        char buffer[FILENAME_MAX + 1];
        snprintf(buffer, FILENAME_MAX, "/proc/self/fd/%d", ff->fd);
    
        ssize_t l = readlink(buffer, ff->filename, FILENAME_MAX);
        if(l == -1)
            snprintf(ff->filename, FILENAME_MAX, "unknown filename for fd %d", ff->fd);
        else
            ff->filename[l] = '\0';
    
        return ff->filename;
    }
    int main() {
        
        char *filename = "/proc/stat";
    
    
        procfile *ff = procfile_open(filename);
        if(ff  == NULL){
        
            return 0;
        }
    
        procfile_filename(ff);
        printf("fd(%d) ---> filename(%s)", ff->fd, ff->filename);
        
        return 0;
    }

![在这里插入图片描述][20210104223238987.png]

[20210104223238987.png]: /images/20221120/ddf2e6fb621f4dc79d7f10a79ba1ae68.png