Skip the Libref: How to Access SAS Data Directly via File Paths

Difficulty Level

Beginner

Published on : 03/01/2024

Expert Advice

Michael
Responsable de l'infrastructure Viya.

The LIBNAME statement is more than just a shortcut; it is a critical layer of abstraction in SAS architecture. While your code demonstrates that direct path access is possible (and useful for one-off tasks or debugging), it bypasses the management benefits of a libref.

Assigning a SAS^© library via the LIBNAME statement allows referencing a physical data location. It is composed of a libref (short name), a library engine (often V9 by default), the folder location, and specific options. Assignments are valid for the current session, unless made persistent. The document details syntax rules, situations where a libref is not necessary, and best practices for efficient SAS^© data management.

Data Analysis

Type : CREATION_INTERNE

Examples use generated data (datalines) or SASHELP.

1 Code Block

LIBNAME statement

Explanation :
This example shows the assignment of a SAS library to a local folder. The `LIBNAME` statement creates a reference (libref 'mylib') pointing to a physical location. We use `V9` as the library engine, which is the default engine for traditional SAS files. Then, a small table `test_data` is created and saved in this library. `PROC PRINT` is used to display the contents of the table. Finally, the library is de-assigned from the SAS session with `LIBNAME mylib clear;`.

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1	/* Crée un dossier temporaire pour la bibliothèque si nécessaire */
2	/* Remplacez 'chemin/vers/votre/bibliotheque' par un chemin réel */
3	/* Pour SAS Viya, cela pourrait être un chemin CAS ou un chemin de système de fichiers accessible */
4	/* Ici, nous utilisons un dossier local simulé pour l'exemple */
5
6	/* Affecte la bibliothèque 'mylib' au chemin spécifié */
7	LIBNAME mylib V9 '%sysfunc(pathname(WORK))/my_sas_library';
8
9	/* Crée une table simple dans la bibliothèque 'mylib' */
10	DATA mylib.test_data;
11	INPUT id name $;
12	DATALINES;
13	1 John
14	2 Jane
15	3 Mike
16	;
17	RUN;
18
19	/* Affiche le contenu de la table */
20	PROC PRINT DATA=mylib.test_data;
21	title 'Contenu de mylib.test_data';
22	RUN;
23
24	/* Désaffecte la bibliothèque */
25	LIBNAME mylib clear;
26

2 Code Block

LIBNAME statement with options

Explanation :
This example illustrates the use of a library option. The 'readonly' libref is assigned to the V9 engine with the `ACCESS=READONLY` option. This means users will only be able to read data from this library, and any attempt to write or modify (like creating 'new_table' in the example) will result in a SAS error. This is useful for protecting data integrity. The code includes a simulation of an existing file so that read-only access makes sense.

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1	/* Affecte une bibliothèque en mode lecture seule */
2	LIBNAME readonly V9 '%sysfunc(pathname(WORK))/my_read_only_library' access=readonly;
3
4	/* Crée une table temporaire pour la démonstration */
5	DATA _null_;
6	file '%sysfunc(pathname(WORK))/my_read_only_library/sample.sas7bdat';
7	put 'This is a sample SAS dataset file.';
8	RUN;
9
10	/* Tente de créer une nouvelle table dans la bibliothèque en lecture seule (va échouer) */
11	DATA readonly.new_table;
12	x=1;
13	RUN;
14
15	/* Désaffecte la bibliothèque */
16	LIBNAME readonly clear;
17

3 Code Block

Direct file access

Explanation :
Although using a libref is recommended, this example shows how to access a SAS table by directly specifying its full path and filename in quotes. This works for many SAS language elements but does not offer the flexibility and advantages of libref management, particularly for engine options and simple path modification.

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1	/* Crée un dossier temporaire pour l'exemple */
2	/* Créons une table SAS temporaire directement dans un chemin */
3	DATA '%sysfunc(pathname(WORK))/my_direct_access_data.sas7bdat';
4	INPUT val;
5	DATALINES;
6	10
7	20
8	30
9	;
10	RUN;
11
12	/* Accède à la table SAS directement par son chemin complet */
13	PROC PRINT DATA='%sysfunc(pathname(WORK))/my_direct_access_data.sas7bdat';
14	title 'Accès direct à la table';
15	RUN;
16
17	/* Note: Le fichier reste sur le disque après la session à moins d'être supprimé explicitement */
18

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