技術標籤：# C++

#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;
}