C: Checking the type of a file. Using lstat() and macros doesn't work
I use opendir() to open a directory and then readdir() and lstat() to get开发者_开发问答 the stats of each file in that directory. Following this manpage I wrote the code under which doesn't work as thought. It does list all the files in the current directory but it doesn't print out whever the file is a regular file, a symlink or a directory.
#include <sys/stat.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
void main(){
char* folder="."; //folder to open
DIR* dir_p;
struct dirent* dir_element;
struct stat file_info;
// open directory
dir_p=opendir(folder);
// show some info for each file in given directory
while(dir_element = readdir(dir_p)){
lstat(dir_element->d_name, &file_info); //getting a file stats
puts(dir_element->d_name); // show current filename
printf("file mode: %d\n", file_info.st_mode);
// print what kind of file we are dealing with
if (file_info.st_mode == S_IFDIR) puts("|| directory");
if (file_info.st_mode == S_IFREG) puts("|| regular file");
if (file_info.st_mode == S_IFLNK) puts("|| symbolic link");
}
}
I Know it is years later but for posterity you were doing it wrong:
@alk was right the st_mode field carries more info e.g file type,file permissions,etc
To extract file type you perform bitwise and on the st_mode field and the file type mask S_IFMT .Then check the result for whatever you wanted. That is what the macros mentioned by @Ernest Friedman-Hill do. A swicth is better suited for a comprehensive check i.e
for a simple case:
if ((file_info.st_mode & S_IFMT)==S_IFDIR) puts("|| directory");
for a comprehensive check:
struct stat st;
...
switch (st.st_mode & S_IFMT) {
case S_IFREG:
puts("|| regular file");
break;
case S_IFDIR:
puts("|| directory");
break;
case S_IFCHR:
puts("|| character device");
break;
case S_IFBLK:
puts("|| block device");
break;
case S_IFLNK:
puts("|| symbolic link");
break;
case S_IFIFO:
puts("|| pipe");
break;
case S_IFSOCK:
puts("|| socket");
break;
default:
puts("|| unknown");
}
There are a set of macros to interpret st_mode
, which is more complex than you think. Use them instead of probing the field directly:
if (S_ISREG(file_info.st_mode))
// file is a regular file
else if (S_ISLNK(file_info.st_mode))
// ...
There's also S_ISDIR
, S_ISSOCK
, and a few more. See, e.g., here for info.
Mode carries lots of info.
Try the following kind of test:
if (S_ISDIR(file_info.st_mode)) puts("|| directory");
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