11   data test;
12      infile "c:\files\test.txt" lrecl=1000;
13      input txt :$1000.;
14      txt_len=length(txt);
15      put "The length of variable is " txt_len;
16   run;

NOTE: The infile "c:\files\test.txt" is:
      File Name=c:\files\test.txt,
      RECFM=V,LRECL=1000

The length of variable is 321
The length of variable is 3
NOTE: 2 records were read from the infile "c:\files\test.txt".
      The minimum record length was 3.
      The maximum record length was 321.
NOTE: The data set WORK.TEST has 2 observations and 2 variables.
NOTE: DATA statement used (Total process time):
      real time           0.01 seconds
      cpu time            0.01 seconds