From: David Combs on 21 Feb 2010 20:29 In article , Ed Morton wrote: snip > >FWIW, here's how I'd really write a script to calculate the min/max/ave from a >set of values being input by a user when prompted: > >\$ cat tst.sh >awk 'BEGIN{ sum=min=max=ave="NAN"; printf "Enter a value: " } >{ > sum += \$0 > min = ( (\$0 < min) || (min == "NAN") ? \$0 : min) > max = ( (\$0 > max) || (max == "NAN") ? \$0 : max) > printf "Enter a value: " >} >END { > ave = ( NR ? sum / NR : ave ) > print "\ntotal =", sum > print "minimum value =", min > print "average value =", ave > print "maximum value =", max >}' >\$ >\$ ./tst.sh >Enter a value: 1 >Enter a value: 2 >Enter a value: >total = 3 >minimum value = 1 >average value = 1.5 >maximum value = 2 >\$ >\$ ./tst.sh >Enter a value: >total = NAN >minimum value = NAN >average value = NAN >maximum value = NAN Try it again, the 2nd group, say, and then as the 4th item enter a NAN, and maybe a 5th as 100 -- whatcha get? What is the user told will happen when he types in a "NAN"? Ignore that entry, forget it even happened? Abort the whole run thus far by assigning every variable a NAN, thus losing the info you'd built up thus far? And then what -- since your initial values were each NAN, keep reading numbers or NAN's, giving him as result whatever you've computed from the most recent run of non-NAN values? Maybe it'd be better to check first for a NAN, and just "continue" if that's what you see -- working out for the user as "the principle of least surprise"? I'm probably wrong somewhere in there, but you can see what I'm trying to get at. David From: Janis Papanagnou on 21 Feb 2010 21:41 David Combs wrote:> In article , > Ed Morton wrote: > ... > ... > >> printf "Enter the number of values to be input: "; read numv; >> >> while (( counter < numv )) > ^ -----^---- The extra paren-pair "hides" the "<" > from being interpreted as a redirection? (Looks like it would.) The (( ... )) construct is an arithmetic command. Within the double brackets you can write math expressions as you would expect, incusive using < > <= >= == != for comparison or using variables without the explicit dereferencing using \$. If using it as a condition in if/while constructs it evaluates to true if the arithmetic expression results in non-zero, otherwise false. Janis > > Not that I know bash ("let"?) -- as bool, does "<" work > on numbers, or must he use ".lt."? > > Silly questions -- maybe those "lets" gave me a concussion! > > > David > > First  |  Prev  |