How to Determine if a Directory Exists in Unix?

Checking Directory Existence in Unix

In Unix, determining the existence of a directory is essential for various operations. Unlike opendir() which only reveals the non-existence of a directory upon an error, there are system calls specifically designed to ascertain the presence of a directory.

To address this need, POSIX systems offer two functions: stat() and lstat(). Both functions provide information about the specified pathname, including its type. However, stat() follows symbolic links while lstat() does not.

To check if a directory exists using stat():

#include <sys/stat.h>

struct stat sb;

if (stat(pathname, &sb) == 0 && S_ISDIR(sb.st_mode)) {
    // Directory exists
}

The macro S_ISDIR() confirms the file type as a directory. Similarly, other file types can be checked using corresponding S_IS* macros.

Conclusion:

stat() and lstat() provide a convenient and comprehensive way to determine the existence and type of a file or directory in Unix, enabling seamless handling of file system-related operations.

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