Checking for File Existence on SAS Drive

The `%mfv_existfile` macro takes a `filepath` parameter (the full path to the file on SAS^© Drive, e.g., /Public/myfile.txt). It uses `%mf_getuniquefileref()` to generate a temporary fileref. The file name and path are extracted from `filepath`. An attempt is made to assign the fileref to the file using the `filename()` function with the 'filesrvc' engine. If the assignment is successful (returns 0), the `fexist()` function is used to confirm the actual existence of the file. If `filename()` fails, the macro returns 0 and ensures that the `&syscc` system macro variable is reset to 0 to avoid masking potential subsequent issues. An initial check of `&syscc` is performed via `%mf_abort` to ensure that the macro is not called in an error state.

Data Analysis

Type : INTERNAL_CREATION

The script neither uses nor creates data in the sense of traditional SAS datasets. Its purpose is to interact with the metadata of the SAS Drive file system to check for the existence of an object (file), whose path is provided as a parameter.

1 Code Block

Macro Call (%mf_abort)

Explanation :
This block calls the `%mf_abort` macro to check if the `&syscc` system macro variable (error return code) is non-zero. If so, it indicates a previous error, and the macro stops, thus avoiding executing the code in an error state.

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1	%mf_abort(
2	iftrue=(&syscc ne 0),
3	msg=Cannot enter mfv_existfile.sas with syscc=&syscc
4	)

2 Code Block

Macro Variable Manipulation

Explanation :
This block declares local macro variables (`fref`, `rc`, `path`, `name`). It initializes `fref` with a unique file reference generated by `%mf_getuniquefileref()`. The `%scan` and `%substr` macro functions are used to extract the file name (`name`) and its path (`path`) from the provided `filepath` parameter.

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1	%local fref rc path name;
2	%let fref=%mf_getuniquefileref();
3	%let name=%scan(&filepath,-1,/);
4	%let path=%substr(&filepath,0,%LENGTH(&filepath)-%LENGTH(&name)-1);

3 Code Block

SAS Functions (filename, fexist)

Explanation :
This conditional block attempts to assign the fileref (`fref`) to the specified file on SAS Drive using the `filename()` function with the `filesrvc` engine. If the assignment is successful (returns 0), `fexist(&fref)` is called to check for the file's existence, and its result is returned. If the assignment fails, the macro returns `0`, and the `&syscc` macro variable is explicitly reset to `0`.

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1	%IF %sysfunc(filename(fref,,filesrvc,folderPath="&path" filename="&name"))=0
2	%THEN %DO;
3	%sysfunc(fexist(&fref))
4	%let rc=%sysfunc(filename(fref));
5	%END;
6	%ELSE %DO;
7	0
8	%let syscc=0;
9	%END;

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Copyright Info : Main author of the `mfv_existfile` macro: Allan Bowe. This macro calls or references distinct and copyrighted components or macros, notably: '_version.sas' (Copyright (c) 2001-2006 Rodney Sparapani) and 'print_macro_parameters.sas' (Copyright © 2022, SAS Institute Inc.).

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