SAS I/O functions (ATTRN( ), ATTRC( ) , EXIST( ), OPEN( ), CLOSE( ) )

SAS provides number of I/O functions which are helpful to retrive metadata information about the sas dataset.

· EXIST(data_set_name) : checks for existence of dataset in the specified library. Returns 1 if data set exists else returns 0.

· OPEN(data_set_name ) : Returns Unique Dataset Identifier number of success else returns 0

· CLOSE(data_set_name) : Returns 0 on success else returns non-zero value.

· OPEN() and CLOSE() are important before doing other operations on SAS dataset. i.e. using functions which retrieve information about the dataset.

· Following functions are very useful to retrieve information about the data set

· ATTRN(datasetID, attributeName)

ATTRN() is used for retrieving numeric information about SAS dataset like number of records, number of variables, creation date etc.

Here datasetID = the unique ID for dataset which is returned by OPEN() function.

We can get information about following numeric attributes using ATTRN()

· NLOBS – It is second attribute for ATTRN( ) function, its gives Number of Logical observations which are not marked for deletion

· NOBS - Number of total observations

· NLOBSF – non deleted obervations that satisfy where clause or obs / Firstobs option.

· CRDDTE – creation time stamp of the dataset

· NVARS – number of variables in the dataset

· INSINDEX - whether or not the dataset is indexed

· ATTRC (datasetId, attributeName)

Similar to ATTRN( ), this function returns value of character attribute of desired data set. Various attribute names are

• • LABEL – Returns dataset label

  • SORTBY – variables name by which dataset is primarily sorted (if sorted at all)

  • MEM – data set name

  • LIB – current library for the dataset

· OPEN -> ATTRN -> ATTRC -> CLOSE

%let data_set = libname.data_set_name;

%let dsid = %sysfunc (open(&data_set));

%let nobs = %sysfunc(attrn(&dsid,nlobs));

%let create_date = %sysfunc(attrn(&dsid, crdte));

%let close_flag = %sysfunc(close(&dsid));