Is there a programmatic way to tell if a symlink points to a file or directory in C?

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I am iterating directories recursively with readdir.

struct dirent is documented here, and notes that d_type can have different values including DT_LNK and DT_DIR and DT_REG. However, when d_type is DT_LNK, there is no hint about whether the link is to a file or directory.

Is there a a way to check whether the target of a symlink is a file or directory?

symlink posix c
1 Answers

The dirent structure might tell you if the entry is a directory or a symbolic link, but some file systems do not provide this information in d_type and set it to DT_UNKNOWN.

In any case, the simplest way to tell if a symbolic link points to a directory or not, is via a stat system call that will resolve the symbolic link and if successful, will populate the stat structure, allowing for S_ISDIR to give you the information:

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

int is_directory(const char *path) {
    struct stat st;
    return !stat(path, &st) && S_ISDIR(st.st_mode);
}

Note these caveats:

  • you must construct the path from the directory name and the entry name to pass to is_directory().
  • recursing on directories linked to by symbolic links may cause infinite recursion as the symbolic link may point to a parent directory or the directory itself where it is located.
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