Storing integer values from string in rrd

You can use awk to handle situations like this. For example, to extract from your rawfile just the 2 SNR and 2 Attn numbers and give them to rrd in the order both downs, then both ups:

awk '/^SNR/  { snrdown = $3; snrup = $4; }
     /^Attn/ { attndown = $2; attnup = $3; }
     END     { data = sprintf("N:%s:%s:%s:%s", snrdown, attndown, snrup, attnup);
               system("rrdtool update " data " myrrdfile");
             }' <rawfile

The first awk line matches only the line beginning "SNR". By default awk splits lines into fields separated by whitespace. Fields are numbered from 1. So $3 is the field with 21.8 in this example. The value is saved in a variable we name arbitrarily.

Similarly, the 2nd awk line matches only the "Attn" line, but since there is no space between that and "(dB)" our first number is in field $2.

The END part is done after all lines have been read from the file rawfile. It creates a string of data for rrd (which needs something like N:21.8:26.0:...). Each %s in the format string is replaced by one of the variables following the format.

awk is well worth getting to know. It is very versatile.