将文件与路径连接以获得C中的完整路径 [英] Concatenating file with path to get full path in C

问题描述

我使用C，试图将目录中的文件名及其路径连接起来，以便可以为每个文件调用stat()，但是当我尝试在循环内使用strcat时，它将前一个文件名与下一个文件名连接起来.它在循环中修改了argv [1]，但是我已经很长时间没有使用C了，所以我很困惑...

Using C, I'm trying to concatenate the filenames in a directory with their paths so that I can call stat() for each, but when I try to do using strcat inside the loop it concatenates the previous filename with the next. It's modifying argv[1] during the loop, but I haven't worked with C in a long time, so I'm very confused...

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <string.h>

int main(int argc, char *argv[]) {
 struct stat buff;

 int status;

 if (argc > 1) {
  status = stat(argv[1], &buff);
  if (status != -1) {
   if (S_ISDIR(buff.st_mode)) { 
     DIR *dp = opendir(argv[1]);
     struct dirent *ep;
     char* path = argv[1];
     printf("Path = %s\n", path);

     if (dp != NULL) {
       while (ep = readdir(dp)) {
       char* fullpath = strcat(path, ep->d_name);
       printf("Full Path = %s\n", fullpath);
     }
     (void) closedir(dp);
   } else {
      perror("Couldn't open the directory");
   }
 }

  } else {
   perror(argv[1]);
   exit(1);
  }
 } else {
   perror(argv[0]]);
                exit(1);
 }

 return 0;
}

推荐答案

您不应修改argv[i].即使您这样做，也只有一个argv[1]，因此对它执行strcat()将会继续追加到先前的内容中.

You shouldn't modify argv[i]. Even if you do, you only have one argv[1], so doing strcat() on it is going to keep appending to whatever you had in it earlier.

您还有另一个细微的错误.在大多数系统上，目录名和文件名应由路径分隔符/分隔.您无需在代码中添加它.

You have another subtle bug. A directory name and file names in it should be separated by the path separator, / on most systems. You don't add that in your code.

要解决此问题，请在while循环之外:

To fix this, outside of your while loop:

size_t arglen = strlen(argv[1]);

您应该在while循环中执行此操作:

You should do this in your while loop:

/* + 2 because of the '/' and the terminating 0 */
char *fullpath = malloc(arglen + strlen(ep->d_name) + 2);
if (fullpath == NULL) { /* deal with error and exit */ }
sprintf(fullpath, "%s/%s", path, ep->d_name);
/* use fullpath */
free(fullpath);

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