SQL - Check access to an IFS file or folder

ifs_access.sql

-- SQL Scalar function to check access to an IFS file or folder

-- It returns:
--    0=If the file or folder Exists and you have access
--   -1=No access or file does not exists 
--
-- This is a wrapper for the access() unix API:
-- https://pubs.opengroup.org/onlinepubs/009695299/functions/access.html

-- Note second parameter is the acces mode, that defaults to F_OK
-- Constants for access() are also declare as SQL global variables  

-- Simply paste this gist into ACS SQL and run it to create the feature.

-- Note: I am using library QUSRSYS. I suggest you put it into your own tool library

-- It is a cool example how far you can go with SQL: Have fun - 
-- (C) Niels Liisberg 2023

-- This gist is distributed on an "as is" basis, without warranties 
-- or conditions of any kind, either express or implied.
----------------------------------------------------------------------------------------------
call qcmdexc ('addlible qsysinc');
--call qcmdexc ('dltf FILE(QTEMP/C) ');
call qcmdexc ('crtsrcpf FILE(QTEMP/C) MBR(C) rcdlen(256)');
truncate qtemp.c;
insert into qtemp.c (srcdta) values 
    ('#include <unistd.h>'), 
    ('IFS_ACCESS.IFS_PATH.DAT[IFS_ACCESS.IFS_PATH.LEN] = 0;'),
    ('MAIN.RC = access ( IFS_ACCESS.IFS_PATH.DAT , IFS_ACCESS.ACCESS_TYPE);')
;
create or replace function  qusrsys.ifs_access  (
    ifs_path    varchar(256) ,
    access_type  int default 0 -- Posix: 0 = F_OK = Test for existence of a file  
)
returns int
specific IFS_ACCESS 
no external action 
set option output=*print, commit=*none, dbgview = *source
main:
begin 
    declare rc int default 0;
    include qtemp/c(c);
    return rc;
end;   

-- Constants for access()  
create or replace variable qusrsys.ifs_access_read    int  default 4; -- R_OK 4
create or replace variable qusrsys.ifs_access_write   int  default 2; -- W_OK 2
create or replace variable qusrsys.ifs_access_execute int  default 1; -- x_OK 1

stop;

-- use case:
------------

-- returns 0 for the home folder - it exists 
values qusrsys.IFS_ACCESS ( 
    ifs_path => '/home'
);


-- returns -1 for files that does not exists 
values qusrsys.IFS_ACCESS ( 
    ifs_path => '/home/does_not_exists'
);

-- returns 0 for the "cat" file exists 
values qusrsys.IFS_ACCESS ( 
    ifs_path => '/bin/cat'
);

-- Can i execute /bin/cat  
values qusrsys.IFS_ACCESS ( 
    ifs_path => '/bin/cat',
    access_type => qusrsys.ifs_access_execute 
);

-- Can i write to home folder
values qusrsys.IFS_ACCESS ( 
    ifs_path => '/home',
    access_type => qusrsys.ifs_access_write 
);