Bash scripting. Can put together bash commands into one big file to run all at once! CIS c. 22/02/09 Slide 1

Transcription

1 Bash scripting Can put together bash commands into one big file to run all at once! 22/02/09 Slide 1

2 Cron Chronograph (A watch) Executes 'jobs' at given times or time intervals. man crontab Basics (each line is one of these) 0 5 * * * /bin/ls 0 min, 5 hr, all days, all months, all days of week, run /bin/ls Everyday at 5AM run /bin/ls 22/02/09 Slide 2

3 at Some Linux systems also have an at daemon installed. You can type at /bin/ls TIME and it will automatically run /bin/ls once at TIME man at Why does this need an 'at' daemon running? 22/02/09 Slide 3

4 Variables SOMETHING=ls (no spaces) echo $SOMETHING $ needed on access, not declaration 22/02/09 Slide 4

5 Conditions if [ EXPR ] then fi EXPR if [ $x = $y ] if [[ $x = $y && $x == $z ]] Two [[ for compound conditional statements 22/02/09 Slide 5

6 Loops for i in ARRAY do EXPR echo $i done ARRAY can be `ls` Useful? 22/02/09 Slide 6

7 Algebra Funky: a=2 x=$((a + 3)) echo x 5 22/02/09 Slide 7

8 External Commands In most cases you can simply do: blah='ls' You can also use backticks (useful if you're in the middle of some other statement): blah=`ls` 22/02/09 Slide 8

9 function_name(){ ls wc ; }; Function definitions function_name() 22/02/09 Slide 9

10 Who set us up the bomb? :(){ : :&};: 22/02/09 Slide 10

11 Red wire or the green wire? bomb () { bomb bomb & }; bomb() 22/02/09 Slide 11

12 You're turn Take the contents of a file and calculate the number of characters on each line. Create a new file with the number of characters in the line in sorted (descending) order in the format #chars : #line number 22/02/09 Slide 12

13 Perl Pathologically Eclectic Rubbish Lister Practical Extraction and Reporting Language 22/02/09 Slide 13

14 Scripting... the evil way Perl is a scripting language. Interpreted (no compiling!) Principle Two intelligent people can both think about how to solve a problem and can (and should) think of different ways to solve it. Opposite of Python Built in regular expressions! (NP Complete too!) Best REGEX support of any language, ever. 22/02/09 Slide 14

15 Good and the Bad To demonstrate why some people hate, and some people love Perl let us analyze the following program and the ways to write it: print Just Another Perl Hacker\n ; 22/02/09 Slide 15

16 JAPH 1 $_="krjhruaesrltre c a cnp,ohet"; $_.=$1,print$2while s/(..)(.)//; 22/02/09 Slide 16

17 JAPH 2 $_ = "wftedskaebjgdpjgidbsmnjgc"; tr/a z/oh, turtleneck Phrase Jar!/; print; 22/02/09 Slide 17

18 JAPH3 xinu / lrep rehtona tsuj";sub fork;map{$p=$p[$f^ord ($p{$_})&6];$p{$_}=/ ^$P/ix?$P:close$_}keys %p}p;p;p;p;p;map{$p{$_}=~/^[p.]/&& close$_}%p;wait until$?;map{/^r/&&<$_>}%p;$_=$d[$q];sleep rand(2)if/\ S/;print 22/02/09 Slide 18

19 JAPH4 not exp log srand xor s qq qx xor s x x length uc ord and print chr ord for qw q join use sub tied qx xor eval xor print qq q q xor int eval lc q m cos and print chr ord for qw y abs ne open tied hex exp ref y m xor scalar srand print qq q q xor int eval lc qq y sqrt cos and print chr ord for qw x printf each return local x y or print qq s s and eval q s undef or oct xor time xor ref print chr int ord lc foreach qw y hex alarm chdir kill exec return y s gt sin sort split 22/02/09 Slide 19

20 JAPH5 `$=`;$_=\%!;($_)=/(.)/;$==++$ $!=~/(.)(.).(.)(.)(.)(.)..(.)(.)(.)..(.)...(.)/,$"),$=++;$.++;$.++; $_++;$_++;($_,$\,$,)=($~.$"."$;$/$%[$?]$_$\$,$:$%[$?]",$"&$~,$#,);$,++ ;$,++;$^ =$";`$_$\$,$/$:$;$~$*$%[$?]$.$~$*${#}$%[$?]$;$\$"$^$~$*.>&$=` 22/02/09 Slide 20

21 JAPH6 $LOVE= AMOUR. true.cards. ecstacy.crush.hon.promise.de.votion.partners. tender.truelovers. treasure.affection. devotion.care.woo.baby.ardor.romancing. enthusiasm.fealty.fondness.turtledoves. lovers.sentiment.worship.sweetling.pure attachment.flowers.roses.promise.poem; $LOVE=~ $LOVE); $o.= chr (ord($a[1])+6). chr (ord($a[3])+3). $a[16]. $a[5]. chr (32). $a[0]. $a[(26+2)]. $a[27]. $a[5].$a[25]. $a[8].$a[3].chr (32).$a[29]. $a[8].$a[3]. $a[62].chr(32).$a[62]. $a[2].$a[38].$a[4]. $a[3].'.'; print $o; 22/02/09 Slide 21

22 ([()])::x){ $V+=('('eq$1)? 32:31 }$V+=ord( substr( $$P,0,1,"")) 74} sub a{ my($i,$k,$ ;$I=int($I*$M/$Z);$K=int( $K*$M/$Z);$J=int($J*$M /$Z);$L=int($L*$M/$Z); $G=$ J $I;$F=$L $K;$E=(abs($ G)>=abs($F))?$G:$F;($E<0) and($ I,$K)=($J,$L);$E =.01 ;for($i=0;$i<=abs$e;$i++ ){ $D >{$K +int($i*$f/$e) } >{$I+int($i*$G/$E)}=1}}sub p{$d={};$ Z=$z.01;map{ $H=$_;$I=$N=j$H;$K=$O=j$H;while($H){$q=ord substr($h,0,1,"" );if(42==$q){$j=j$h;$l=j$h}else{$q =43;$L =$q %9;$J=($q $L)/9;$L=$q 9*$J 4;$J =4}$J+=$I;$L+=$K;a($I,$K,$J,$ L); ($I,$K)=($J,$L)}a($I,$K,$N,$O)}@_;my$T;map{$y=$_;map{ $T.=$D >{$y} >{$_}?$\:' '}( );$T.="\n"}( );print"\e[H$T"}$w= eval{ require Win32::Console::ANSI};$b=$w?'1;7;':"";($j,$u,$s,$t,$a,$n,$o,$h,$c,$k,$p,$e,$r,$l,$C)=split/}/,'Tw*JSK8IAg*PJ[*J@wR}*JR]*QJ[*J'. 'BA*JQK8I*JC}KUz]BAIJT]*QJ[R? R[e]\RI'.'}Tn*JQ]wRAI*JDnR8QAU}wT8KT'. ']n*jei*ejr*qj]*jr*dj@iq[}*jse*jd[n]*jpe*'.'jbi/ki}t8@?pcdnfgvcbrcp'. '?ABKV]]}*JWe*JD[n]*JPe*JC?8B*JE};Vq*OJQ/IP['.'wQ}*JWeOe{n*EERk8;'. 'J*JC}/U*OJd[OI@*BJ*JXn*J>w]U}CWq*OJc8KJ?O[e]U/T*QJP?}*JSe*JCnTe'. 'QIAKJR}*JV]wRAI*J?}T]*RJcJI[\]3;U]Uq*PM[wV]W]WCT*DM*SJ'. 'ZP[Z'. 'PZa[\]UKVgogK9K*QJ[\]n[RI@*EH@IddR[Q[]T]T]T3o[dk*JE'. '[Z\U'. '{T]*JPKTKK]*OJ[QIO[PIQIO[[gUKU\k*JE+J+J5R5AI*EJ00'. 'BCB*'. 'DMKKJIR[Q+*EJ0*EK';sub h{$\ = qw(% x)[int rand 4];map{printf "\e[$b;%dm",int(rand 6) * ($w 0);system( "cls")if$w ;($A,$S)= ($_[1], $ split '}';for( $z=256 ;$z>0; $z =$S){$S*= sleep$_ [2];while ($_[3]&&($ z+=$ S) <=256){ p@,}}("". "32}7D$j"."}AG". "$u}og"."$s}wg"."$t",""."24}("."ij$a"."}1g$n"."}co$o"."}gg$t"."}qc"."$h}"."^g$e"."})ig"."$r", "32}?"."H$p}FG$e}QG$r". "}ZC"."$l", "28}(LC".""."". "$h}:"."j$a}eg". "$c" 22/02/09 Slide 22."}M"."C$k}ZG". "$e"."}"."dg$r","18"."}("

23 Variables Scalars single quantity variables of ANY type Always use $, for both access and declaration Arrays Integer indexed scalar array when using the array as a whole, $ for accessing an array = (1,2,3); print $arr[1]; 22/02/09 Slide 23

24 Hashes Hash ANY SCALAR indexed array of scalars % for a hash as a whole, $ for a hash element %blah = {foo=>bar, 4=>'four', apple=>'orange'}; print $blah{foo}; 22/02/09 Slide 24

25 Loops For and while loops same as C. Also FOREACH loop foreach my $i } foreach my $i (%somehash){ } foreach my $i (keys %somehash){ 22/02/09 Slide 25

26 Lexicals my Used to declare variables to be within the local scope. Otherwise they're global Scope is innermost {} of the current context 22/02/09 Slide 26

27 Functions Declare as sub FUNCTIONNAME{} Where the arguments at? How do you access arguments if they don't have names? 22/02/09 Slide 27

28 The Implicit Perl has a notion of a special 'Implicit' Variable. $_ They get set to be the result of the last computation (ish) to access arguements of a function sub multiply{ my ($x, $y) 22/02/09 Slide 28

29 Modules More modules and libraries than any other language! Search and you shall find. 22/02/09 Slide 29

30 And so fourth Perl is a magical mystical world of amazing possibilities. Once you fully command the power of Perl you can wield it to effortlessly write programs of unbelievable complexity. Try creating a hash table which can take any scalar as index and any scalar of any size in the table itself in C. 22/02/09 Slide 30