Most of my knowledge of cat comes from: a) man page b) a class where one of the subjects was programming in awk (and other tools) c) web search for particular cases, problems, or examples :)
Perhaps googling for "awk howto" or "awk programming" etc... However, it's probably not worth investing a lot of time in awk unless you really have to (grades, salary, etc...) Rui On Mon, Jul 27, 2009 at 10:57:42AM +0200, Davide Scaini wrote: > ok, thanks! (i'll try to reduce my useless cats) > but awk syntax is really "awkward" ;-) do you know a bright guide for awk? > (please not man awk...) > d > > On Sun, Jul 26, 2009 at 10:12 PM, Rui Miguel Silva Seabra > <[email protected]>wrote: > > > Because you launched 1 program then 4 programs in background, which > > are fed to a while loop => much memory + cpu usage. > > > > With... opkg list_upgradable | awk '!/(kernel|Multiple)/ {print $1}' > > > > ... you now launch less 3 programs than before (two greps and one cat), > > while feeding exactly the same output to the while loop. :) > > > > If you grep then awk or awk then grep, then 99% of the time you're > > uselessly greping. Awk greps better than grep, specially when you > > want to transform the output :) > > > > Also a nice read: Useless use of cat > > http://www.google.pt/search?q=useless+use+of+cat > > > > Rui > > > > On Sun, Jul 26, 2009 at 09:40:26PM +0200, Davide Scaini wrote: > > > he he this is the power of opensource... > > > why you said that is heavy? (i just want to learn, i'm quite newbie in > > > scripting and expecially using awk...) > > > d > > > > > > On Sun, Jul 26, 2009 at 8:29 PM, Rui Miguel Silva Seabra <[email protected] > > >wrote: > > > > > > > On Sun, Jul 26, 2009 at 07:18:07PM +0100, Rui Miguel Silva Seabra > > wrote: > > > > > On Sun, Jul 26, 2009 at 07:49:19PM +0200, Davide Scaini wrote: > > > > > > I want to share my little bash script to update shr without > > distroying > > > > my > > > > > > existing kernel (a true 2.6.28). > > > > > > It's really stupid, but maybe someone could find it interesting. > > > > > > > > > > > > opkg list_upgradable > upgradable > > > > > > > > > > > > cat upgradable | awk '{print $1}' | grep -v kernel | grep -v > > Multiple | > > > > > > while read line > > > > > > > > > > > > do echo "installing pack $line" > > > > > > opkg install $line > > > > > > done > > > > > > > > > > > > I have a script called upgrade.sh and I run that one. If you don't > > want > > > > to > > > > > > update for example tangogps (or wathever) just add > > > > > > grep -v tangogps | > > > > > > just before "while read line"... > > > > > > > > > > Nice. But a little heavy on the little Neos :) May I suggest a > > possible > > > > > alternative? > > > > > > > > oops a mistake, this one is corrected, though: > > > > > > > > opkg list_upgradable | awk '!/(kernel|Multiple)/ {print $1}' | \ > > > > while read line; do > > > > echo "installing pack $line" > > > > opkg install $line > > > > done > > > > > > > > Rui > > > > > > > > _______________________________________________ > > > > Openmoko community mailing list > > > > [email protected] > > > > http://lists.openmoko.org/mailman/listinfo/community > > > > > > > > > _______________________________________________ > > > Openmoko community mailing list > > > [email protected] > > > http://lists.openmoko.org/mailman/listinfo/community > > > > > > -- > > > > _______________________________________________ > > Openmoko community mailing list > > [email protected] > > http://lists.openmoko.org/mailman/listinfo/community > > > _______________________________________________ > Openmoko community mailing list > [email protected] > http://lists.openmoko.org/mailman/listinfo/community -- _______________________________________________ Openmoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
