feat: get_cwd and set_cwd (fortran-lang#1014)

Author: perazz

doc/specs/stdlib_system.md

@@ -646,6 +646,80 @@ Subroutine
 
 ---
 
+## `get_cwd` - Gets the current working directory
+
+### Status
+
+Experimental
+
+### Description
+
+This subroutine retrieves the current working directory the running process is executing from.
+It is designed to work across multiple platforms. On Windows, paths with both forward `/` and backward `\` slashes are accepted.
+
+### Syntax
+
+`call [[stdlib_system(module):get_cwd(subroutine)]] (cwd [, err])`
+
+### Class
+
+Subroutine
+
+### Arguments
+
+`cwd`: Shall be a character string for receiving the path of the current working directory (cwd). It is an `intent(out)` argument.
+
+`err`(optional): Shall be of type `state_type`, and is used for error handling. It is an `intent(out)` argument.
+
+### Return values
+
+`err` is an optional state return flag. On error if not requested, an `FS_ERROR` will trigger an error stop.
+
+### Example
+
+```fortran
+{!example/system/example_cwd.f90!}
+```
+
+---
+
+## `set_cwd` - Sets the current working directory
+
+### Status
+
+Experimental
+
+### Description
+
+This subrotine sets the current working directory the process is executing from.
+It is designed to work across multiple platforms. On Windows, paths with both forward `/` and backward `\` slashes are accepted.
+
+### Syntax
+
+`call [[stdlib_system(module):set_cwd(subroutine)]] (path [, err])`
+
+### Class
+
+Subroutine
+
+### Arguments
+
+`path`: Shall be a character string containing the path of the directory. It is an `intent(in)` argument.
+
+`err`(optional): Shall be of type `state_type`, and is used for error handling. It is an `intent(out)` argument.
+
+### Return values
+
+`err` is an optional state return flag. On error if not requested, an `FS_ERROR` will trigger an error stop.
+
+### Example
+
+```fortran
+{!example/system/example_cwd.f90!}
+```
+
+---
+
 ## `null_device` - Return the null device file path
 
 ### Status
@@ -682,6 +756,8 @@ None.
 {!example/system/example_null_device.f90!}
 ```
 
+---
+
 ## `delete_file` - Delete a file
 
 ### Status
@@ -723,6 +799,8 @@ The file is removed from the filesystem if the operation is successful. If the o
 {!example/system/example_delete_file.f90!}
 ```
 
+---
+
 ## `join_path` - Joins the provided paths according to the OS
 
 ### Status
@@ -785,6 +863,8 @@ The result is an `allocatable` character string or `type(string_type)`
 {!example/system/example_path_join.f90!}
 ```
 
+---
+
 ## `split_path` - splits a path immediately following the last separator
 
 ### Status
@@ -825,6 +905,8 @@ The splitted path. `head` and `tail`.
 {!example/system/example_path_split_path.f90!}
 ```
 
+---
+
 ## `base_name` - The last part of a path
 
 ### Status
@@ -860,6 +942,8 @@ A character string or `type(string_type)`.
 {!example/system/example_path_base_name.f90!}
 ```
 
+---
+
 ## `dir_name` - Everything except the last part of the path
 
 ### Status

example/system/CMakeLists.txt

@@ -18,3 +18,4 @@ ADD_EXAMPLE(path_base_name)
 ADD_EXAMPLE(path_dir_name)
 ADD_EXAMPLE(make_directory)
 ADD_EXAMPLE(remove_directory)
+ADD_EXAMPLE(cwd)

example/system/example_cwd.f90

@@ -0,0 +1,32 @@
+! Illustrate the usage of `get_cwd`, `set_cwd`
+program example_cwd
+    use stdlib_system, only: get_cwd, set_cwd
+    use stdlib_error, only: state_type
+    implicit none 
+
+    character(len=:), allocatable :: path
+    type(state_type) :: err
+
+    call get_cwd(path, err)
+
+    if (err%error()) then
+        print *, "Error getting current working directory: "//err%print()
+    end if
+    
+    print *, "CWD: "//path
+
+    call set_cwd("./src", err)
+
+    if (err%error()) then
+        print *, "Error setting current working directory: "//err%print()
+    end if
+
+    call get_cwd(path, err)
+
+    if (err%error()) then
+        print *, "Error getting current working directory after using set_cwd: "//err%print()
+    end if
+    
+    print *, "CWD: "//path
+end program example_cwd
+

src/stdlib_system.F90

@@ -2,7 +2,7 @@ module stdlib_system
 use, intrinsic :: iso_c_binding, only : c_int, c_long, c_ptr, c_null_ptr, c_int64_t, c_size_t, &
     c_f_pointer
 use stdlib_kinds, only: int64, dp, c_bool, c_char
-use stdlib_strings, only: to_c_char, find
+use stdlib_strings, only: to_c_char, find, to_string
 use stdlib_string_type, only: string_type
 use stdlib_optval, only: optval
 use stdlib_error, only: state_type, STDLIB_SUCCESS, STDLIB_FS_ERROR
@@ -156,6 +156,32 @@ module stdlib_system
 !!
 public :: remove_directory
 
+!! version: experimental
+!!
+!! Gets the current working directory of the process
+!! ([Specification](../page/specs/stdlib_system.html#get_cwd))
+!!
+!! ### Summary
+!! Gets the current working directory.
+!!
+!! ### Description
+!! This subroutine gets the current working directory the process is executing from.
+!!
+public :: get_cwd
+
+!! version: experimental
+!!
+!! Sets the current working directory of the process
+!! ([Specification](../page/specs/stdlib_system.html#set_cwd))
+!!
+!! ### Summary
+!! Changes the current working directory to the one specified.
+!!
+!! ### Description
+!! This subroutine sets the current working directory the process is executing from.
+!!
+public :: set_cwd
+
 !! version: experimental
 !!
 !! Deletes a specified file from the filesystem.
@@ -896,6 +922,25 @@ end function stdlib_is_directory
 
 end function is_directory
 
+! A Helper function to convert C character arrays to Fortran character strings
+function to_f_char(c_str_ptr, len) result(f_str)
+    type(c_ptr), intent(in) :: c_str_ptr
+    ! length of the string excluding the null character
+    integer(kind=c_size_t), intent(in) :: len
+    character(:), allocatable :: f_str
+
+    integer :: i
+    character(kind=c_char), pointer :: c_str(:)
+
+    call c_f_pointer(c_str_ptr, c_str, [len])
+
+    allocate(character(len=len) :: f_str)
+
+    do concurrent (i=1:len)
+        f_str(i:i) = c_str(i)
+    end do
+end function to_f_char
+
 ! A helper function to get the result of the C function `strerror`.
 ! `strerror` is a function provided by `<string.h>`. 
 ! It returns a string describing the meaning of `errno` in the C header `<errno.h>`
@@ -911,18 +956,11 @@ end function strerror
     end interface
 
     type(c_ptr) :: c_str_ptr
-    integer(c_size_t) :: len, i
-    character(kind=c_char), pointer :: c_str(:)
+    integer(c_size_t) :: len
 
     c_str_ptr = strerror(len)
 
-    call c_f_pointer(c_str_ptr, c_str, [len])
-
-    allocate(character(len=len) :: str)
-
-    do concurrent (i=1:len)
-        str(i:i) = c_str(i)
-    end do
+    str = to_f_char(c_str_ptr, len)
 end function c_get_strerror
 
 !! makes an empty directory
@@ -1024,6 +1062,56 @@ end function stdlib_remove_directory
 
 end subroutine remove_directory
 
+subroutine get_cwd(cwd, err)
+    character(:), allocatable, intent(out) :: cwd
+    type(state_type), optional, intent(out) :: err
+    type(state_type) :: err0
+
+    interface
+        type(c_ptr) function stdlib_get_cwd(len, stat) bind(C, name='stdlib_get_cwd')
+            import c_ptr, c_size_t
+            integer(c_size_t), intent(out) :: len
+            integer :: stat
+        end function stdlib_get_cwd
+    end interface
+
+    type(c_ptr) :: c_str_ptr
+    integer(c_size_t) :: len
+    integer :: stat
+
+    c_str_ptr = stdlib_get_cwd(len, stat)
+
+    if (stat /= 0) then
+        err0 = FS_ERROR_CODE(stat, c_get_strerror())
+        call err0%handle(err)
+    end if
+
+    cwd = to_f_char(c_str_ptr, len)
+
+end subroutine get_cwd
+
+subroutine set_cwd(path, err)
+    character(len=*), intent(in) :: path
+    type(state_type), optional, intent(out) :: err
+    type(state_type) :: err0
+
+    interface
+        integer function stdlib_set_cwd(path) bind(C, name='stdlib_set_cwd')
+            import c_char
+            character(kind=c_char), intent(in) :: path(*)
+        end function stdlib_set_cwd
+    end interface
+
+    integer :: code
+
+    code = stdlib_set_cwd(to_c_char(trim(path)))
+
+    if (code /= 0) then
+        err0 = FS_ERROR_CODE(code, c_get_strerror())
+        call err0%handle(err)
+    end if
+end subroutine set_cwd
+
 !> Returns the file path of the null device for the current operating system.
 !>
 !> Version: Helper function.
@@ -1042,21 +1130,13 @@ end function process_null_device
 
     end interface
 
-    integer(c_size_t) :: i, len
+    integer(c_size_t) :: len
     type(c_ptr) :: c_path_ptr
-    character(kind=c_char), pointer :: c_path(:)    
 
     ! Call the C function to get the null device path and its length
     c_path_ptr = process_null_device(len)
-    call c_f_pointer(c_path_ptr,c_path,[len])
 
-    ! Allocate the Fortran string with the length returned from C
-    allocate(character(len=len) :: path)
-        
-    do concurrent (i=1:len)
-        path(i:i) = c_path(i)
-    end do
-        
+    path = to_f_char(c_path_ptr, len)
 end function null_device
 
 !> Delete a file at the given path.

src/stdlib_system.c

@@ -1,4 +1,6 @@
+#include <limits.h>
 #include <stddef.h>
+#include <stdlib.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <string.h>
@@ -44,3 +46,48 @@ int stdlib_remove_directory(const char* path){
 
     return (!code) ? 0 : errno;
 }
+
+// Wrapper to the platform's `getcwd`(get current working directory) call.
+// Uses `getcwd` on unix, `_getcwd` on windows.
+// Returns the cwd, sets the length of cwd and the `stat` of the operation.
+char* stdlib_get_cwd(size_t* len, int* stat){
+    *stat = 0;
+#ifdef _WIN32
+    char* buffer;
+    buffer = _getcwd(NULL, 0);
+
+    if (buffer == NULL) {
+        *stat = errno;
+        return NULL;
+    }
+
+    *len = strlen(buffer);
+    return buffer;
+#else
+    char buffer[PATH_MAX + 1];
+    if (!getcwd(buffer, sizeof(buffer))) {
+        *stat = errno;
+    }
+
+    *len = strlen(buffer);
+
+    char* res = malloc(*len);
+    strncpy(res, buffer, *len);
+
+    return res;
+#endif /* ifdef _WIN32 */
+}
+
+// Wrapper to the platform's `chdir`(change directory) call.
+// Uses `chdir` on unix, `_chdir` on windows.
+// Returns 0 if successful, otherwise returns the `errno`.
+int stdlib_set_cwd(char* path) {
+    int code;
+#ifdef _WIN32
+    code = _chdir(path);
+#else
+    code = chdir(path);
+#endif /* ifdef _WIN32 */
+    
+    return (code == -1) ? errno : 0;
+}