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sprintfFORMAT,LIST

ReturnsastringformattedbytheusualprintfconventionsoftheClibraryfunctionsprintf.Seebelowformoredetailsandseesprintf(3)orprintf(3)onyoursystemforanexplanationofthegeneralprinciples.

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Forexample:

1. #Formatnumberwithupto8leadingzeroes2. $result=sprintf("%08d",$number);3.4. #Roundnumberto3digitsafterdecimalpoint5. $rounded=sprintf("%.3f",$number);

Perldoesitsownsprintfformatting:itemulatestheCfunctionsprintf(3),butdoesn'tuseitexceptforfloatingpointnumbers,andeventhenonlystandardmodifiersareallowed.Nonstandardextensionsinyourlocalsprintf(3)arethereforeunavailablefromPerl.

Unlikeprintf,sprintfdoesnotdowhatyouprobablymeanwhenyoupassitanarrayasyourfirstargument.Thearrayisgivenscalarcontext,andinsteadofusingthe0thelementofthearrayastheformat,Perlwillusethecountofelementsinthearrayastheformat,whichisalmostneveruseful.

Perl'ssprintfpermitsthefollowinguniversallyknownconversions:

1. %%apercentsign2. %cacharacterwiththegivennumber3. %sastring4. %dasignedinteger,indecimal5. %uanunsignedinteger,indecimal6. %oanunsignedinteger,inoctal7. %xanunsignedinteger,inhexadecimal8. %eafloatingpointnumber,inscientificnotation9. %fafloatingpointnumber,infixeddecimalnotation

10. %gafloatingpointnumber,in%eor%fnotation

Inaddition,Perlpermitsthefollowingwidelysupportedconversions:

1. %Xlike%x,butusinguppercaseletters2. %Elike%e,butusinganuppercase"E"3. %Glike%g,butwithanuppercase"E"(ifapplicable)4. %banunsignedinteger,inbinary5. %Blike%b,butusinganuppercase"B"withthe#flag6. %papointer(outputsthePerlvalue'saddressinhexadecimal)7. %nspecial:*stores*thenumberofcharactersoutputsofar8. intothenextargumentintheparameterlist

Finally,forbackward(andwedomean"backward")compatibility,Perlpermitstheseunnecessarybutwidelysupportedconversions:

1. %iasynonymfor%d2. %Dasynonymfor%ld3. %Uasynonymfor%lu4. %Oasynonymfor%lo5. %Fasynonymfor%f

Notethatthenumberofexponentdigitsinthescientificnotationproducedby%e,%E,%gand%Gfornumberswiththemodulusoftheexponentlessthan100issystemdependent:itmaybethreeorless(zeropaddedasnecessary).Inotherwords,1.23timestentothe99thmaybeeither"1.23e99"or"1.23e099".

Betweenthe%andtheformatletter,youmayspecifyseveraladditionalattributescontrollingtheinterpretationoftheformat.Inorder,theseare:

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formatparameterindex

Anexplicitformatparameterindex,suchas2$.Bydefaultsprintfwillformatthenextunusedargumentinthelist,butthisallowsyoutotaketheargumentsoutoforder:

1. printf'%2$d%1$d',12,34;#prints"3412"2. printf'%3$d%d%1$d',1,2,3;#prints"311"

flags

oneormoreof:

1. spaceprefixnonnegativenumberwithaspace2. +prefixnonnegativenumberwithaplussign3. leftjustifywithinthefield4. 0usezeros,notspaces,torightjustify5. #ensuretheleading"0"foranyoctal,6. prefixnonzerohexadecimalwith"0x"or"0X",7. prefixnonzerobinarywith"0b"or"0B"

Forexample:

1. printf'',12;#prints""2. printf'',12;#prints""3. printf'',12;#prints""4. printf'',12;#prints""5. printf'',12;#prints""6. printf'',12;#prints""7. printf'',12;#prints""8. printf'',12;#prints""9. printf'',12;#prints""

10. printf'',12;#prints""

Whenaspaceandaplussignaregivenastheflagsatonce,aplussignisusedtoprefixapositivenumber.

1. printf'',12;#prints""2. printf'',12;#prints""

Whenthe#flagandaprecisionaregiveninthe%oconversion,theprecisionisincrementedifit'snecessaryfortheleading"0".

1. printf'',012;#prints""2. printf'',012345;#prints""3. printf'',0;#prints""

vectorflag

ThisflagtellsPerltointerpretthesuppliedstringasavectorofintegers,oneforeachcharacterinthestring.Perlappliestheformattoeachintegerinturn,thenjoinstheresultingstringswithaseparator(adot.bydefault).Thiscanbeusefulfordisplayingordinalvaluesofcharactersinarbitrarystrings:

1. printf"%vd","AB\x{100}";#prints"65.66.256"2. printf"versionisv%vd\n",$^V;#Perl'sversion

Putanasterisk*beforethevtooverridethestringtousetoseparatethenumbers:

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1. printf"addressis%*vX\n",":",$addr;#IPv6address2. printf"bitsare%0*v8b\n","",$bits;#randombitstring

Youcanalsoexplicitlyspecifytheargumentnumbertouseforthejoinstringusingsomethinglike*2$vforexample:

1. printf'%*4$vX%*4$vX%*4$vX',#3IPv6addresses2. @addr[1..3],":";

(minimum)width

Argumentsareusuallyformattedtobeonlyaswideasrequiredtodisplaythegivenvalue.Youcanoverridethewidthbyputtinganumberhere,orgetthewidthfromthenextargument(with*)orfromaspecifiedargument(e.g.,with*2$):

1. printf"","a";#prints""2. printf"","a";#prints""3. printf"",6,"a";#prints""4. printf'',"a",6;#prints""5. printf"","long";#prints""(doesnottruncate)

Ifafieldwidthobtainedthrough*isnegative,ithasthesameeffectastheflag:leftjustification.

precision,ormaximumwidth

Youcanspecifyaprecision(fornumericconversions)oramaximumwidth(forstringconversions)byspecifyinga.followedbyanumber.ForfloatingpointformatsexceptgandG,thisspecifieshowmanyplacesrightofthedecimalpointtoshow(thedefaultbeing6).Forexample:

1. #theseexamplesaresubjecttosystemspecificvariation2. printf'',1;#prints""3. printf'',1;#prints""4. printf'',1;#prints""5. printf'',10;#prints""6. printf'',10;#prints""

For"g"and"G",thisspecifiesthemaximumnumberofdigitstoshow,includingthosepriortothedecimalpointandthoseafteritforexample:

1. #Theseexamplesaresubjecttosystemspecificvariation.2. printf'',1;#prints""3. printf'',1;#prints""4. printf'',100;#prints""5. printf'',100;#prints""6. printf'',100.01;#prints""7. printf'',100.01;#prints""8. printf'',100.01;#prints""

Forintegerconversions,specifyingaprecisionimpliesthattheoutputofthenumberitselfshouldbezeropaddedtothiswidth,wherethe0flagisignored:

1. printf'',1;#prints""2. printf'',1;#prints""3. printf'',1;#prints""4. printf'',1;#prints""

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5. printf'',1;#prints""6. printf'',1;#prints""7.8. printf'',1;#prints""9. printf'',1;#prints""

10. printf'',1;#prints""11. printf'',1;#prints""12. printf'',1;#prints""13. printf'',1;#prints""

Forstringconversions,specifyingaprecisiontruncatesthestringtofitthespecifiedwidth:

1. printf'',"truncated";#prints""2. printf'',"truncated";#prints""

Youcanalsogettheprecisionfromthenextargumentusing.*:

1. printf'',1;#prints""2. printf'',6,1;#prints""

Ifaprecisionobtainedthrough*isnegative,itcountsashavingnoprecisionatall.

1. printf'',7,"string";#prints""2. printf'',3,"string";#prints""3. printf'',0,"string";#prints""4. printf'',1,"string";#prints""5.6. printf'',1,0;#prints""7. printf'',0,0;#prints""8. printf'',1,0;#prints""

Youcannotcurrentlygettheprecisionfromaspecifiednumber,butitisintendedthatthiswillbepossibleinthefuture,forexampleusing.*2$:

1. printf'',1,6;#INVALID,butinfuturewillprint2. #""

size

Fornumericconversions,youcanspecifythesizetointerpretthenumberasusingl,h,V,q,L,orll.Forintegerconversions(duoxXbiDUO),numbersareusuallyassumedtobewhateverthedefaultintegersizeisonyourplatform(usually32or64bits),butyoucanoverridethistouseinsteadoneofthestandardCtypes,assupportedbythecompilerusedtobuildPerl:

1. hhinterpretintegerasCtype"char"or"unsigned2. char"onPerl5.14orlater3. hinterpretintegerasCtype"short"or4. "unsignedshort"5. jinterpretintegerasCtype"intmax_t"onPerl6. 5.14orlater,andonlywithaC99compiler7. (unportable)8. linterpretintegerasCtype"long"or9. "unsignedlong"

10. q,L,orllinterpretintegerasCtype"longlong",11. "unsignedlonglong",or"quad"(typically12. 64bitintegers)13. tinterpretintegerasCtype"ptrdiff_t"onPerl

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14. 5.14orlater15. zinterpretintegerasCtype"size_t"onPerl5.1416. orlater

Asof5.14,noneoftheseraisesanexceptioniftheyarenotsupportedonyourplatform.However,ifwarningsareenabled,awarningoftheprintfwarningclassisissuedonanunsupportedconversionflag.Shouldyouinsteadpreferanexception,dothis:

1. usewarningsFATAL=>"printf";

Ifyouwouldliketoknowaboutaversiondependencybeforeyoustartrunningtheprogram,putsomethinglikethisatitstop:

1. use5.014;#forhh/j/t/z/printfmodifiers

YoucanfindoutwhetheryourPerlsupportsquadsviaConfig:

1. useConfig;2. if($Config{use64bitint}eq"define"3. ||$Config{longsize}>=8){4. print"Nicequads!\n";5. }

Forfloatingpointconversions(efgEFG),numbersareusuallyassumedtobethedefaultfloatingpointsizeonyourplatform(doubleorlongdouble),butyoucanforce"longdouble"withq,L,orllifyourplatformsupportsthem.YoucanfindoutwhetheryourPerlsupportslongdoublesviaConfig:

1. useConfig;2. print"longdoubles\n"if$Config{d_longdbl}eq"define";

YoucanfindoutwhetherPerlconsiders"longdouble"tobethedefaultfloatingpointsizetouseonyourplatformviaConfig:

1. useConfig;2. if($Config{uselongdouble}eq"define"){3. print"longdoublesbydefault\n";4. }

Itcanalsobethatlongdoublesanddoublesarethesamething:

1. useConfig;2. ($Config{doublesize}==$Config{longdblsize})&&3. print"doublesarelongdoubles\n";

ThesizespecifierVhasnoeffectforPerlcode,butissupportedforcompatibilitywithXScode.Itmeans"usethestandardsizeforaPerlintegerorfloatingpointnumber",whichisthedefault.

orderofarguments

Normally,sprintf()takesthenextunusedargumentasthevaluetoformatforeachformatspecification.Iftheformatspecificationuses*torequireadditionalarguments,theseareconsumedfromtheargumentlistintheordertheyappearintheformatspecificationbeforethevaluetoformat.Whereanargumentisspecifiedbyanexplicitindex,thisdoesnotaffect

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thenormalorderforthearguments,evenwhentheexplicitlyspecifiedindexwouldhavebeenthenextargument.

So:

1. printf"",$a,$b,$c;

uses$aforthewidth,$bfortheprecision,and$casthevaluetoformatwhile:

1. printf'',$a,$b;

woulduse$aforthewidthandprecision,and$basthevaluetoformat.

Herearesomemoreexamplesbeawarethatwhenusinganexplicitindex,the$mayneedescaping:

1. printf"%2\$d%d\n",12,34;#willprint"3412\n"2. printf"%2\$d%d%d\n",12,34;#willprint"341234\n"3. printf"%3\$d%d%d\n",12,34,56;#willprint"561234\n"4. printf"%2\$*3\$d%d\n",12,34,3;#willprint"3412\n"

Ifuselocale(includinguselocale'not_characters')isineffectandPOSIX::setlocale()hasbeencalled,thecharacterusedforthedecimalseparatorinformattedfloatingpointnumbersisaffectedbytheLC_NUMERIClocale.SeeperllocaleandPOSIX.

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