implement is_directory

Author: perazz

src/stdlib_system.F90

@@ -1,6 +1,7 @@
 module stdlib_system
 use, intrinsic :: iso_c_binding, only : c_int, c_long, c_null_ptr, c_int64_t
-use stdlib_kinds, only: int64, dp
+use stdlib_kinds, only: int64, dp, c_bool, c_char
+use stdlib_strings, only: to_c_char
 implicit none
 private
 public :: sleep
@@ -81,6 +82,22 @@ module stdlib_system
 public :: elapsed
 public :: is_windows
 
+!! version: experimental
+!!
+!! Tests if a given path matches an existing directory.
+!! ([Specification](../page/specs/stdlib_io.html#is_directory-test-if-a-path-is-a-directory))
+!!
+!!### Summary
+!! Function to evaluate whether a specified path corresponds to an existing directory.
+!!
+!!### Description
+!! 
+!! This function checks if a given file system path is a directory. It is cross-platform and avoids reliance 
+!! on external C libraries by utilizing system calls. It supports common operating systems such as Linux, macOS, 
+!! Windows, and various UNIX-like environments. On unsupported operating systems, the function will return `.false.`.
+!!
+public :: is_directory
+     
 ! CPU clock ticks storage
 integer, parameter, private :: TICKS = int64
 integer, parameter, private :: RTICKS = dp
@@ -618,4 +635,23 @@ pure function OS_NAME(os)
     end select
 end function OS_NAME
 
+!! Tests if a given path matches an existing directory.
+!! Cross-platform implementation without using external C libraries.
+logical function is_directory(path)
+    !> Input path to evaluate
+    character(*), intent(in) :: path
+
+    interface
+        
+        logical(c_bool) function stdlib_is_directory(path) bind(c, name="stdlib_is_directory")
+            import c_bool, c_char
+            character(kind=c_char), intent(in) :: path(*)
+        end function stdlib_is_directory
+
+    end interface        
+    
+    is_directory = logical(stdlib_is_directory(to_c_char(path)))
+    
+end function is_directory
+
 end module stdlib_system

src/stdlib_system_subprocess.F90

@@ -1,7 +1,7 @@
 submodule (stdlib_system) stdlib_system_subprocess
     use iso_c_binding  
     use iso_fortran_env, only: int64, real64
-    use stdlib_strings, only: to_c_char, join
+    use stdlib_strings, only: join
     use stdlib_linalg_state, only: linalg_state_type, LINALG_ERROR, linalg_error_handling
     implicit none(type, external)
 

src/stdlib_system_subprocess.c

@@ -10,6 +10,7 @@
 #else
 #define _POSIX_C_SOURCE 199309L
 #include <sys/wait.h>
+#include <sys/stat.h>  
 #include <unistd.h>
 #include <time.h>
 #include <errno.h>
@@ -220,6 +221,12 @@ bool process_kill_windows(stdlib_pid pid) {
     return true;
 }
 
+// Check if input path is a directory
+bool stdlib_is_directory_windows(const char *path) {
+    DWORD attrs = GetFileAttributesA(path);
+    return    (attrs != INVALID_FILE_ATTRIBUTES)  // Path exists
+           && (attrs & FILE_ATTRIBUTE_DIRECTORY); // Path is a directory
+}
 
 #else // _WIN32
 
@@ -292,12 +299,29 @@ void process_create_posix(stdlib_pid* pid)
     (*pid) = (stdlib_pid) fork();
 }
 
+// On UNIX systems: check if input path is a directory
+bool stdlib_is_directory_posix(const char *path) {
+    struct stat sb;
+    return stat(path, &sb) == 0 && S_ISDIR(sb.st_mode);
+}
+
 #endif // _WIN32
 
 /////////////////////////////////////////////////////////////////////////////////////
 // Cross-platform interface
 /////////////////////////////////////////////////////////////////////////////////////
 
+// Cross-platform interface: query directory state
+bool stdlib_is_directory(const char *path) {
+    // Invalid input
+    if (path == NULL || strlen(path) == 0) return false;  
+#ifdef _WIN32
+    return stdlib_is_directory_windows(path);
+#else
+    return stdlib_is_directory_posix(path);
+#endif // _WIN32
+}
+
 // Create or fork process
 void process_create(const char* cmd, const char* stdin_stream, const char* stdin_file, 
                     const char* stdout_file, const char* stderr_file,