WFDB

sampfreq <filename> ~ Get the sampling frequency
rdsamp -r s20011 | head ~ Print the first 10 lines of the record

              0	     55	     81
              1	     55	     84
              2	     55	     87
              3	     56	     89
              4	     57	     91
              5	     61	     93
              6	     65	     95
              7	     67	     99
              8	     69	    103
              9	     72	    105

rdsamp -r s20011 -t 0:00:02.00 | less ~ Print the first 2 seconds of the record
Plot samples using octave

rdsamp -r s20011 -f 0 -t 0:00:02.00 > sample.txt # Store the first 2 seconds of the record in a file
gnuplot
plot "sample.txt" using 1:3 with lines # x-axis: 1st column, y-axis: 3rd column
replot "sample.txt" using 1:2 with lines # x-axis: 1st column, y-axis: 2nd column

Or save the plot

gnuplot
set term png
set output "sample.png"
plot "sample.txt" u 1:2 w l, "sample.txt" u 1:3 w l

rdann -r s20011 -a atr | more ~ Print annotations; explanation of annotations.
wrann -r s20011 -a qrs < s20011.asc ~ Write annotations to file
wfdb2mat -r s20011 -f 0 -t 12 ~ Convert to matlab format
wfdb2mat -r s20011 -f 0 -t 12 > s20011m.info ~ Save the stdout info in a file, matlab needs it for plotting