EXIST Function

Verifies the existence of a SAS data library member

Category: SAS File I/O

Syntax

EXIST ( member- name < ,member-type < , generation >>)

Arguments

member-name

specifies the SAS data library member. If member-name is blank or a null string, then EXIST uses the value of the _LAST_ system variable as the member-name .

member-type

specifies the type of SAS data library member. A few common member types are ACCESS, CATALOG, DATA, and VIEW. If you do not specify a member-type , then the member type DATA is assumed.

generation

specifies the generation number of the SAS data set whose existence you are checking. If member-type is not DATA, generation is ignored.

Positive numbers are absolute references to a historical version by its generation number. Negative numbers are relative references to a historical version in relation to the base version, from the youngest predecessor to the oldest. For example, -1 refers to the youngest version or, one version back from the base version. Zero is treated as a relative generation number.

Details

EXIST returns 1 if the library member exists, or 0 if member-name does not exist or member-type is invalid. Use CEXIST to verify the existence of an entry in a catalog.

Examples

Example 1: Verifying the Existence of a Data Set

This example verifies the existence of a data set. If the data set does not exist, then the example displays a message in the log:

 %let dsname=sasuser.houses;  %macro opends(name);  %if %sysfunc(exist(&name)) %then     %let dsid=%sysfunc(open(&name,i));  %else %put Data set &name does not exist.;  %mend opends;  %opends(&dsname);

Example 2: Verifying the Existence of a Data View

This example verifies the existence of the SAS data view TEST.MYVIEW. If the view does not exist, then the example displays a message in the log:

 data _null_;  dsname="test.myview";     if (exist(dsname,"VIEW")) then        dsid=open(dsname,"i");     else put dsname 'does not exist.';  run;

Example 3: Determining If a Generation Data Set Exists

This example verifies the existence of a generation data set by using positive generation numbers (absolute reference):

 data new(genmax=3);     x=1;  run;  data new;     x=99;  run;  data new;     x=100;  run;  data new;     x=101;  run;  data _null_;     test=exist('new', 'DATA', 4);     put test=;     test=exist('new', 'DATA', 3);     put test=;     test=exist('new', 'DATA', 2);     put test=;     test=exist('new', 'DATA', 1);     put test=;  run;

These lines are written to the SAS log:

 test=1  test=1  test=1  test=0

You can change this example to verify the existence of the generation data set by using negative numbers (relative reference):

 data new2(genmax=3);     x=1;  run;  data new2;     x=99;  run;  data new2;     x=100;  run;  data new2;     x=101;  run;  data _null_;     test=exist('new2', 'DATA', 0);     put test=;     test=exist('new2', 'DATA', -1);     put test=;     test=exist('new2', 'DATA', -2);     put test=;     test=exist('new2', 'DATA', -3);     put test=;     test=exist('new2', 'DATA', -4);     put test=;  run;