UNIX for Dummies Questions & Answers

Hi all...

In the OSX forum I am starting a new awk project to learn awk.

In this code snippet I have had to check boundaries to ensure that no NUMERICAL error occurs in the rest of the code...

Code:

	printf "Enter frequency required:- ";
	getline FREQ;
	RATE=(BYTES*FREQ);
	if ( RATE <= 4000 ) { RATE=4000 };
	if ( RATE >= 48000 ) { RATE=48000 };
	return RATE;

What I don't understand however, is when I enter random characters I expect an error, but instead I get the RATE set to '4000' and it keeps working.
Can one of you awk experts explain what is happening and/or why?

Many thanks in advance...

If FREQ is garbage, its numerical value is zero by design with awk, then RATE is zero too, finally RATE being less than 4000 is set to 4000.

try, add line after getline:

Code:

if (! (FREQ+=0)) return 0;

To detect random input, I'd rather add this test after getline:

Code:

if(FREQ !=0 && FREQ+0==0) { printf("Invalid frequency: [%s]\n",FREQ); exit 1 ; }

Note that all your lines are ended by a semicolon but this is not needed with awk. Unlike with C, an end of line is already ending a command so the semicolon is only required to delimit multiple commands on a single line.

Hi jlliagre...

Thanks a lot this makes for easier coding...

I was observing this and was not sure if it was a _feature_ of awk.

I searched all over and could not find anything on the WWW so my last port of call was to ask.

I don't need to detect a user error as it cycles to KB access and a 'QUIT' command anyhow...

Again thanks...