feat(io): Add exists function for checking file or directory existence

API-doc-FORD-file.md

@@ -17,6 +17,9 @@ exclude: src/stdlib_linalg_lapack.fypp
          src/stdlib_linalg_lapack_w.fypp
          src/stdlib_linalg_lapack_z.fypp
 fpp_extensions: fypp
+extensions: f90
+            F90
+            fypp
 preprocess: true
 macro: MAXRANK=3
        PROJECT_VERSION_MAJOR=0

doc/specs/stdlib_io.md

@@ -260,3 +260,32 @@ Provides formats for all kinds as defined in the `stdlib_kinds` module.
 ```fortran
 {!example/io/example_fmt_constants.f90!}
 ```
+
+## `exists`
+
+### Status
+
+Experimental
+
+### Description
+
+Check if a file or directory exists.
+Returns `.true.` if the file or directory exists, `.false.` otherwise.
+
+### Syntax
+
+`exists = ` [[stdlib_io_path(module):exists(function)]] `(path)`
+
+### Arguments
+
+`path`: Shall be a character expression containing the path to the file or directory to check.
+
+### Return value
+
+The result is a scalar of type `logical`. `.true.` if the file or directory exists, `.false.` otherwise.
+
+### Example
+
+```fortran
+{!example/io/example_exists.f90!}
+```

example/io/CMakeLists.txt

@@ -1,3 +1,4 @@
+ADD_EXAMPLE(exists)
 ADD_EXAMPLE(fmt_constants)
 #ADD_EXAMPLE(getline)
 ADD_EXAMPLE(loadnpy)

example/io/example_exists.f90

@@ -0,0 +1,14 @@
+program example_exists
+
+    use stdlib_io_path, only: exists
+    implicit none
+    integer :: fh
+
+    open (newunit=fh, file='example_exists.txt')
+    print *, exists('example_exists.txt')   ! .true.
+    close (fh, status="delete")
+
+    print *, exists('example_exists.txt')   ! .false.
+    print *, exists('./doc/specs/')         ! Check if directory exists
+
+end program example_exists

src/CMakeLists.txt

@@ -108,6 +108,7 @@ set(SRC
     stdlib_hashmaps.f90
     stdlib_hashmap_chaining.f90
     stdlib_hashmap_open.f90
+    stdlib_io_path.F90
     stdlib_logger.f90
     stdlib_sorting_radix_sort.f90
     stdlib_system.F90

src/stdlib_io_path.F90

@@ -0,0 +1,30 @@
+! SPDX-Identifier: MIT
+
+!> This module implements some useful functions on pathnames.
+!> To read or write files see [open()](../page/specs/stdlib_io.html#open),
+!> and for accessing the filesystem see the [os](../page/specs/stdlib_io.html) module.
+!> ([Specification](../page/specs/stdlib_io.html))
+module stdlib_io_path
+
+    implicit none
+    private
+
+    public :: exists
+
+contains
+
+    !> Version: experimental
+    !>
+    !> Check if a file or directory exists
+    !> ([Specification](../page/specs/stdlib_io.html#exists))
+    logical function exists(path)
+        character(len=*), intent(in) :: path
+
+        inquire (file=path, exist=exists)
+#ifdef __INTEL_COMPILER
+        if (.not. exists) inquire (directory=path, exist=exists)
+#endif
+
+    end function exists
+
+end module stdlib_io_path

test/io/CMakeLists.txt

@@ -16,4 +16,5 @@ set_tests_properties(savetxt_qp PROPERTIES LABELS quadruple_precision)
 ADDTEST(getline)
 ADDTEST(npy)
 ADDTEST(open)
+ADDTEST(path)
 ADDTEST(parse_mode)

test/io/test_path.f90

@@ -0,0 +1,64 @@
+module test_path
+
+    use stdlib_io_path, only: exists
+    use testdrive, only: new_unittest, unittest_type, error_type, check
+    implicit none
+    private
+
+    public :: collect_path
+
+contains
+
+    !> Collect all exported unit tests
+    subroutine collect_path(testsuite)
+        !> Collection of tests
+        type(unittest_type), allocatable, intent(out) :: testsuite(:)
+
+        testsuite = [ &
+                    new_unittest("path_exists", test_path_exists) &
+                    ]
+
+    end subroutine collect_path
+
+    subroutine test_path_exists(error)
+        !> Error handling
+        type(error_type), allocatable, intent(out) :: error
+        integer :: fh
+
+        open (newunit=fh, file='test_path_exists.txt')
+        call check(error, exists('test_path_exists.txt'))
+        close (fh, status="delete")
+
+        call check(error,.not. exists('test_path_exists.txt.not'))
+
+    end subroutine test_path_exists
+
+end module test_path
+
+program tester
+
+    use, intrinsic :: iso_fortran_env, only: error_unit
+    use testdrive, only: run_testsuite, new_testsuite, testsuite_type
+    use test_path, only: collect_path
+    implicit none
+    integer :: stat, is
+    type(testsuite_type), allocatable :: testsuites(:)
+    character(len=*), parameter :: fmt = '("#", *(1x, a))'
+
+    stat = 0
+
+    testsuites = [ &
+                 new_testsuite("path", collect_path) &
+                 ]
+
+    do is = 1, size(testsuites)
+        write (error_unit, fmt) "Testing:", testsuites(is)%name
+        call run_testsuite(testsuites(is)%collect, error_unit, stat)
+    end do
+
+    if (stat > 0) then
+        write (error_unit, '(i0, 1x, a)') stat, "test(s) failed!"
+        error stop
+    end if
+
+end program tester