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1、5)?Input?and?Output?Ma-?Webster?IMBIM,?BMC?ma-hew.webster@imbim.uu.se?reading?from???standard?input?=?the?keyboard??standard?output?=?the?screen?–can?be?redirected?to?a??le?using?>?in?unixwhile($line=){!!print"youtyped$line";!}!!or?!while(){!!print"youtyped$_";!}!reading?f
2、rom???an?important?di?erence?while(){}!#?will?read?from?standard?input?one?line?at?a?Nme?!foreach(){}!#?will?read?everything?from?standard?input?before?looping?#?not?a?good?idea?to?use?this...?!reading?from?<>??the?diamond?operator??can?be?used?to?make?programs?that?proces
3、s??les?like?unixcommands??e.g.?on?the?command?line?you?could?type?./perl_script.plmy_file.txt!my_file.txtcould?accessed?fromperl_script.pl!using??while(<>){}!!but?it?is?oPen?be-er?to?use?a??lehandle?(see?later)?@ARGV??it?is?common?to?run?programs?with?invocaNon?arguments??these?are?just?values
4、?coming?aPer?the?program?name.?e.g.?./perl_script.pl-s-v500!the?values?are?place?in?@ARGV?$arg1=shift@ARGV;!#?$arg1?contains?‐s?$arg2=shift@ARGV;!#?$arg2?contains?–v?$arg3=shift@ARGV;!#?$arg3?contains?500?output?to?standard?output?print@array;???#?no?interpolaNon?is?not?the?same?as?print"@arra
5、y";????#?interpolaNon?print@array?prints?the?list?with?no?spaces?between?print"@array"?performs?interpolaNon??STDOUT?is?normally?the?screen,?it?is?redirected?in?unix?with?>!?if?you?print?to?STDERR?(standard?error),?it?will?not?be?redirected?by?>!printf!?can?be?used?to?format?output??most?usefu
6、l?to?print?numbers?with?decimal?places?printf"piisabout%d",3.1415126;!piisabout3!!print"5millionis%e",5000000!5millionis5e+6!!printf"piiscloserto%f1.2",3.1415126;!piiscloserto3.14!!?a?code?is?placed?in?the?string?to?format?the?values?coming?aPer?printf!Format?Result?%%?A?percent?sign??%s
7、?A?string?%d?A?signed?integer?(decimal)??A??oaNng?point?number?%e?(scienN?c?notaNon)?A??oaNng?point?number?(?xed?%f?decimal?notaNon)?A??oaNng?point?number?(%e?%g?or?%f?notaNon?according?to?value?size)?Filehandles?Very?useful?for?reading
