Understanding FILENAME in SAS: The Key to External File Management

Synopsis

The FILENAME statement in SAS is a powerful tool used for assigning a fileref (file reference) to an external file or device, enabling seamless data input and output operations within SAS programs.

Documentation

The FILENAME statement is essential for managing external files in SAS. By creating a fileref, users can reference external files (such as text files, CSVs, or spreadsheets) without specifying the full path each time. This flexibility simplifies file handling and enhances code portability.

Purpose

• To create a logical reference to an external file or device.
• To manage file access for reading and writing data.
• To enable the use of external data sources within SAS procedures.

Usage

The basic syntax for the FILENAME statement is as follows:

FILENAME fileref 'external-file-path';

• fileref: A user-defined name (up to 8 characters) that represents the external file.
• external-file-path: The complete path to the file or device, enclosed in single or double quotes.

Options

The FILENAME statement can also include multiple options:

• DISK: Specifies the file is on disk.
• TEMP: Indicates the file is temporary and will be deleted after the SAS session ends.
• URL: Allows access to files on the web.

Examples

Example 1: Basic FILENAME Usage

FILENAME myfile '/path/to/your/data.txt';
DATA mydata;
    INFILE myfile;
    INPUT var1 var2 var3;
RUN;

In this example, the FILENAME statement assigns the fileref myfile to a text file located at /path/to/your/data.txt. The DATA step then reads data from this file.

Example 2: Using TEMP Option

FILENAME tempfile TEMP;
DATA _NULL_;
    FILE tempfile;
    PUT 'This is a temporary file.';
RUN;

Here, tempfile is a temporary file that will be deleted at the end of the session. The DATA step writes a line of text to it.

Example 3: Accessing a URL

FILENAME myurl URL 'http://example.com/data.csv';
PROC IMPORT DATAFILE=myurl OUT=mydata DBMS=CSV REPLACE;
RUN;

This example demonstrates how to read a CSV file from a URL using the FILENAME statement.

Explanation

When using the FILENAME statement, users should be mindful of the following:

• Ensure the file path is correct; otherwise, SAS will raise an error.
• Filerefs are case-sensitive on some operating systems (like UNIX), so consistency is key.
• Always remember to free up filerefs using FILENAME fileref CLEAR; when they are no longer needed, especially in long-running sessions or applications.
• Temporary files created with the TEMP option will not be accessible outside the current SAS session.

One Line Summary

The FILENAME statement in SAS is used to assign a logical reference to an external file, streamlining data input and output operations.