Convert a String In C To Upper Case

Question

How could one convert a string to upper case  The examples I have found from googling only have to deal with chars

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Here is the latest code with C  11  std  string cmd    Hello World   for each cmd begin    cmd end       char amp  in   in     toupper in

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include  lt string gt   include  lt locale gt   std  string str    Hello World    auto  amp  f   std  use facet lt std  ctype lt char gt  gt  std  locale     f toupper str data    str data     str size       This will perform better than all the answers that use the global toupper function  and is presumably what boost  to upper is doing underneath   This is because   toupper has to look up the locale - because it might ve been changed by a different thread - for every invocation  whereas here only the call to locale   has this penalty  And looking up the locale generally involves taking a lock   This also works with C  98 after you replace the auto  use of the new non-const str data    and add a space to break the template closing       to        like this   std  use facet lt std  ctype lt char gt   gt   amp  f        std  use facet lt std  ctype lt char gt   gt  std  locale     f toupper const cast lt char   gt  str data     str data     str size

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typedef std  string  value type char t   char t up char  char t ch         return std  use facet lt  std  ctype lt  char t  gt   gt   std  locale     toupper  ch       std  string toupper  const std  string  amp src         std  string result      std  transform  src begin    src end    std  back inserter  result    up char        return result     const std  string src     test test TEST    std  cout  lt  lt  toupper  src

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I use this solution    I know you re not supposed to modify that data area     but I think that s mostly for buffer overrun bugs and null character     upper casing things isn t the same   void to upper const std  string str        std  string  iterator it      int i      for   i 0 i lt str size     i               char    void   str data    i  toupper   char   str data    i

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include  lt algorithm gt   include  lt string gt   std  string str    Hello World   std  transform str begin    str end   str begin      toupper

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not sure there is a built in function   Try this   Include either the ctype h OR cctype libraries  as well as the stdlib h as part of the preprocessor directives    string StringToUpper string strToConvert     change each element of the string to upper case    for unsigned int i 0 i lt strToConvert length   i               strToConvert i    toupper strToConvert i            return strToConvert   return the converted string    string StringToLower string strToConvert     change each element of the string to lower case    for unsigned int i 0 i lt strToConvert length   i               strToConvert i    tolower strToConvert i            return strToConvert   return the converted string

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The answer of  dirkgently is very inspiring  but I want to emphasize that due to the concern as is shown below   Like all other functions from   the behavior of std  toupper is undefined if the argument s value is neither representable as unsigned char nor equal to EOF  To use these functions safely with plain chars  or signed chars   the argument should first be converted to unsigned char  Reference  std  toupper  As the standard does not specify if plain char is signed or unsigned 1   the correct usage of std  toupper should be   include  lt algorithm gt   include  lt cctype gt   include  lt iostream gt   include  lt iterator gt   include  lt string gt   void ToUpper std  string amp  input        std  for each std  begin input   std  end input      char amp  c            c   static cast lt char gt  std  toupper static cast lt unsigned char gt  c                int main         std  string s   quot Hello world  quot         std  cout  lt  lt  s  lt  lt  std  endl        ToUpper s       std  cout  lt  lt  s  lt  lt  std  endl       return 0     Output  Hello world  HELLO WORLD

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The faster one if you use only ASCII characters  for i 0 str i   0 i      if str i  lt   z   amp  amp  str i  gt   a       str i    A - a    Please note that this code run faster but only works on ASCII and is not an  quot abstract quot  solution  Extended version for other UTF8 alphabets      if str i  lt   z   amp  amp  str i  gt   a     is latin     str i    A - a   else if str i  lt       amp  amp  str i  gt         cyrillic     str i      -    else if str i  lt       amp  amp  str i  gt   a     greek     str i    O -      etc     If you need full UNICODE solutions or more conventional and abstract solutions  go for other answers and work with methods of C   strings

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The following works for me    include  lt algorithm gt  void  toUpperCase std  string amp  str        std  transform str begin    str end    str begin      toupper      int main        std  string str    hello      toUpperCase  amp str

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Use a lambda  std  string s  quot change my case quot     std  locale locale  auto to upper     amp locale   char ch    return std  use facet lt std  ctype lt char gt  gt  locale  toupper ch       std  transform s begin    s end    s begin    to upper

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template lt size t size gt  char  toupper char   amp dst  size   const char  src           generate mapping table once     static char maptable 256       static bool mapped      if   mapped            for  char c   0  c  lt  256  c                  if  c  gt    a   amp  amp  c  lt    z                   maptable c    c  amp  0xdf              else                 maptable c    c                    mapped   true                use mapping table to quickly transform text     for  int i   0   src  amp  amp  i  lt  size  i              dst i    maptable   src                return dst

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As long as you are fine with ASCII-only and you can provide a valid pointer to RW memory  there is a simple and very effective one-liner in C   void strtoupper char  str         while   str    str      toupper  unsigned char  str       This is especially good for simple strings like ASCII identifiers which you want to normalize into the same character-case  You can then use the buffer to construct a std string instance

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This problem is vectorizable with SIMD for the ASCII character set       Speedup comparisons   Preliminary testing with x86-64 gcc 5 2 -O3 -march native on a Core2Duo  Merom    The same string of 120 characters  mixed lowercase and non-lowercase ASCII   converted in a loop 40M times  with no cross-file inlining  so the compiler can t optimize away or hoist any of it out of the loop    Same source and dest buffers  so no malloc overhead or memory cache effects  data is hot in L1 cache the whole time  and we re purely CPU-bound    boost  to upper copy lt char   std  string gt      198 0s   Yes  Boost 1 58 on Ubuntu 15 10 is really this slow   I profiled and single-stepped the asm in a debugger  and it s really  really bad   there s a dynamic cast of a locale variable happening per character      dynamic cast takes multiple calls to strcmp    This happens with LANG C and with LANG en CA UTF-8   I didn t test using a RangeT other than std  string   Maybe the other form of to upper copy optimizes better  but I think it will always new malloc space for the copy  so it s harder to test   Maybe something I did differs from a normal use-case  and maybe normally stopped g   can hoist the locale setup stuff out of the per-character loop   My loop reading from a std  string and writing to a char dstbuf 4096  makes sense for testing  loop calling glibc toupper  6 67s   not checking the int result for potential multi-byte UTF-8  though   This matters for Turkish   ASCII-only loop  8 79s   my baseline version for the results below    Apparently a table-lookup is faster than a cmov  with the table hot in L1 anyway  ASCII-only auto-vectorized  2 51s    120 chars is half way between worst case and best case  see below  ASCII-only manually vectorized  1 35s   See also this question about toupper   being slow on Windows when a locale is set     I was shocked that Boost is an order of magnitude slower than the other options   I double-checked that I had -O3 enabled  and even single-stepped the asm to see what it was doing   It s almost exactly the same speed with clang   3 8   It has huge overhead inside the per-character loop   The perf record   report result  for the cycles perf event  is     32 87   flipcase-clang-  libstdc   so 6 0 21        ZNK10  cxxabiv121  vmi class type info12  do dyncastElNS 17  class type info10  sub kindEPKS1 PKvS4 S6 RNS1 16   21 90   flipcase-clang-  libstdc   so 6 0 21         dynamic cast                                                                                                    16 06   flipcase-clang-  libc-2 21 so                GI   strcmp ssse3                                                                                                8 16   flipcase-clang-  libstdc   so 6 0 21        ZSt9use facetISt5ctypeIcEERKT RKSt6locale                                                                         7 84   flipcase-clang-  flipcase-clang-boost       Z16strtoupper boostPcRKNSt7  cxx1112basic stringIcSt11char traitsIcESaIcEEE                                       2 20   flipcase-clang-  libstdc   so 6 0 21       strcmp plt                                                                                                         2 15   flipcase-clang-  libstdc   so 6 0 21         dynamic cast plt                                                                                                 2 14   flipcase-clang-  libstdc   so 6 0 21        ZNKSt6locale2id5 M idEv                                                                                           2 11   flipcase-clang-  libstdc   so 6 0 21        ZNKSt6locale2id5 M idEv plt                                                                                       2 08   flipcase-clang-  libstdc   so 6 0 21        ZNKSt5ctypeIcE10do toupperEc                                                                                      2 03   flipcase-clang-  flipcase-clang-boost       ZSt9use facetISt5ctypeIcEERKT RKSt6locale plt                                                                     0 08          Autovectorization  Gcc and clang will only auto-vectorize loops when the iteration count is known ahead of the loop    i e  search loops like plain-C implementation of strlen won t autovectorize    Thus  for strings small enough to fit in cache  we get a significant speedup for strings  128 chars long from doing strlen first   This won t be necessary for explicit-length strings  like C   std  string       char  not int  is essential  otherwise gcc unpacks to vectors of int   Huge slowdown  char ascii toupper char char c        return   a   lt   c  amp  amp  c  lt    z     c 0x20   c          autovectorizes to PXOR  runs on more ports than paddb       gcc can only auto-vectorize loops when the number of iterations is known before the first iteration   strlen gives us that size t strtoupper autovec char  dst  const char  src        size t len   strlen src       for  size t i 0   i lt len     i            dst i    ascii toupper char src i        gcc does the vector range check with psubusb   pcmpeqb instead of pcmpgtb           return len      Any decent libc will have an efficient strlen that s much faster than looping a byte at a time  so separate vectorized strlen and toupper loops are faster   Baseline  a loop that checks for a terminating 0 on the fly   Times for 40M iterations  on a Core2  Merom  2 4GHz   gcc 5 2 -O3 -march native    Ubuntu 15 10    dst    src  so we make a copy   but they don t overlap  and aren t nearby    Both are aligned    15 char string  baseline  1 08s  autovec  1 34s 16 char string  baseline  1 16s  autovec  1 52s 127 char string  baseline  8 91s  autovec  2 98s      non-vector cleanup has 15 chars to process 128 char string  baseline  9 00s  autovec  2 06s 129 char string  baseline  9 04s  autovec  2 07s      non-vector cleanup has 1 char to process   Some results are a bit different with clang   The microbenchmark loop that calls the function is in a separate file    Otherwise it inlines and strlen   gets hoisted out of the loop  and it runs dramatically faster  esp  for 16 char strings  0 187s    This has the major advantage that gcc can auto-vectorize it for any architecture  but the major disadvantage that it s slower for the usually-common case of small strings     So there are big speedups  but compiler auto-vectorization doesn t make great code  esp  for cleanup of the last up-to-15 characters   Manual vectorization with SSE intrinsics   Based on my case-flip function that inverts the case of every alphabetic character   It takes advantage of the  unsigned compare trick   where you can do low  lt  a  amp  amp  a  lt   high with a single unsigned comparison by range shifting  so that any value less than low wraps to a value that s greater than high    This works if low and high aren t too far apart      SSE only has a signed compare-greater  but we can still use the  unsigned compare  trick by range-shifting to the bottom of the signed range  Subtract  a  128  so the alphabetic characters range from -128 to -128 25  -128  z - a    Note that adding 128 and subtracting 128 are the same thing for 8bit integers   There s nowhere for the carry to go  so it s just xor  carryless add   flipping the high bit    include  lt immintrin h gt     m128i upcase si128   m128i src           The above 2 paragraphs were comments here       m128i rangeshift    mm sub epi8 src   mm set1 epi8  a  128          m128i nomodify      mm cmpgt epi8 rangeshift   mm set1 epi8 -128   25        0 lower case   -1 anything else  upper case or non-alphabetic    25    z  -  a         m128i flip     mm andnot si128 nomodify   mm set1 epi8 0x20                  0x20 lcase    0 non-lcase         just mask the XOR-mask so elements are XORed with 0 instead of 0x20     return           mm xor si128 src  flip          it s easier to xor with 0x20 or 0 than to AND with  0x20 or 0xFF     Given this function that works for one vector  we can call it in a loop to process a whole string   Since we re already targeting SSE2  we can do a vectorized end-of-string check at the same time   We can also do much better for the  cleanup  of the last up-to-15 bytes left over after doing vectors of 16B   upper-casing is idempotent  so re-processing some input bytes is fine   We do an unaligned load of the last 16B of the source  and store it into the dest buffer overlapping the last 16B store from the loop   The only time this doesn t work is when the whole string is under 16B  Even when dst src  non-atomic read-modify-write is not the same thing as not touching some bytes at all  and can break multithreaded code   We have a scalar loop for that  and also to get src aligned   Since we don t know where the terminating 0 will be  an unaligned load from src might cross into the next page and segfault   If we need any bytes in an aligned 16B chunk  it s always safe to load the whole aligned 16B chunk   Full source  in a github gist      FIXME  doesn t always copy the terminating 0     microbenchmarks are for this version of the code  with  mm store in the loop  instead of storeu  for Merom   size t strtoupper sse2 char  dst  const char  src begin        const char  src   src begin         scalar until the src pointer is aligned     while    0xf  amp   uintptr t src   amp  amp   src               dst      ascii toupper   src                 if    src          return src - src begin          current position  p  is now 16B-aligned  and we re not at the end     int zero positions      do             m128i sv    mm load si128   const   m128i  src               TODO  SSE4 2 PCMPISTRI or PCMPISTRM version to combine the lower-case and   0  detection             m128i nullcheck    mm cmpeq epi8  mm setzero si128    sv           zero positions    mm movemask epi8 nullcheck              TODO  unroll so the null-byte check takes less overhead         if  zero positions              break             m128i upcased   upcase si128 sv        doing this before the loop break lets gcc realize that the constants are still in registers for the unaligned cleanup version   But it leads to more wasted insns in the early-out case           mm storeu si128    m128i  dst  upcased              mm store si128    m128i  dst  upcased       for testing on CPUs where storeu is slow         src    16          dst    16        while 1           handle the last few bytes   Options  scalar loop  masked store  or unaligned 16B         rewriting some bytes beyond the end of the string would be easy         but doing a non-atomic read-modify-write outside of the string is not safe         Upcasing is idempotent  so unaligned potentially-overlapping is a good option       unsigned int cleanup bytes   ffs zero positions  - 1      excluding the trailing null     const char  last byte   src   cleanup bytes      points at the terminating   0          FIXME  copy the terminating 0 when we end at an aligned vector boundary        optionally special-case cleanup bytes    15  final aligned vector can be used      if  cleanup bytes  gt  0            if  last byte - src begin  gt   16                   if src  dest  this load overlaps with the last store   store-forwarding stall   Hopefully OOO execution hides it               m128i sv    mm loadu si128   const   m128i   last byte-15        includes the  0              mm storeu si128    m128i   dst   cleanup bytes - 15   upcase si128 sv              else                  whole string less than 16B                if this is common  try 64b or even 32b cleanup with movq   movd and upcase si128  if 1             for  unsigned int i   0   i  lt   cleanup bytes     i                    dst i    ascii toupper src i                   else                gcc stupidly auto-vectorizes this  resulting in huge code bloat  but no measurable slowdown because it never runs             for  int i   cleanup bytes - 1    i  gt   0   --i                    dst i    ascii toupper src i                   endif                      return last byte - src begin      Times for 40M iterations  on a Core2  Merom  2 4GHz   gcc 5 2 -O3 -march native    Ubuntu 15 10    dst    src  so we make a copy   but they don t overlap  and aren t nearby    Both are aligned    15 char string  baseline  1 08s  autovec  1 34s   manual  1 29s 16 char string  baseline  1 16s  autovec  1 52s   manual  0 335s 31 char string  manual  0 479s 127 char string  baseline  8 91s  autovec  2 98s  manual  0 925s 128 char string  baseline  9 00s  autovec  2 06s  manual  0 931s 129 char string  baseline  9 04s  autovec  2 07s  manual  1 02s    Actually timed with  mm store in the loop  not  mm storeu  because storeu is slower on Merom even when the address is aligned   It s fine on Nehalem and later   I ve also left the code as-is for now  instead of fixing the failure to copy the terminating 0 in some cases  because I don t want to re-time everything    So for short strings longer than 16B  this is dramatically faster than auto-vectorized   Lengths one-less-than-a-vector-width don t present a problem   They might be a problem when operating in-place  because of a store-forwarding stall    But note that it s still fine to process our own output  rather than the original input  because toupper is idempotent    There s a lot of scope for tuning this for different use-cases  depending on what the surrounding code wants  and the target microarchitecture   Getting the compiler to emit nice code for the cleanup portion is tricky   Using ffs 3   which compiles to bsf or tzcnt on x86  seems to be good  but obviously that bit needs a re-think since I noticed a bug after writing up most of this answer  see the FIXME comments    Vector speedups for even smaller strings can be obtained with movq or movd loads stores   Customize as necessary for your use-case     UTF-8   We can detect when our vector has any bytes with the high bit set  and in that case fall back to a scalar utf-8-aware loop for that vector   The dst point can advance by a different amount than the src pointer  but once we get back to an aligned src pointer  we ll still just do unaligned vector stores to dst   For text that s UTF-8  but mostly consists of the ASCII subset of UTF-8  this can be good  high performance in the common case with correct behaviour in all cases   When there s a lot of non-ASCII  it will probably be worse than staying in the scalar UTF-8 aware loop all the time  though     Making English faster at the expense of other languages is not a future-proof decision if the downside is significant     Locale-aware   In the Turkish locale  tr TR   the correct result from toupper  i   is  I   U0130   not  I   plain ASCII    See Martin Bonner s comments on a question about tolower   being slow on Windows   We can also check for an exception-list and fallback to scalar there  like for multi-byte UTF8 input characters   With this much complexity  SSE4 2 PCMPISTRM or something might be able to do a lot of our checks in one go

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std  string value  for  std  string  iterator p   value begin    value end      p    p       p   toupper  p

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std  string str    quot STriNg oF mIxID CasE lETteRS quot   C   11  Using for each std  for each str begin    str end       char  amp  c   c     toupper c        Using transform std  transform str begin    str end    str begin      toupper     C    Winodws Only   strupr s str  str length      C    Using Boost Library  boost  to upper copy str

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You can simply use this in C  17 for auto i   str  putchar toupper i

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If you are only concerned with 8 bit characters  which all other answers except Milan Babu  kov assume as well  you can get the fastest speed by generating a look-up table at compile time using metaprogramming  On ideone com this runs 7x faster than the library function and 3x faster than a hand written version  http   ideone com sb1Rup   It is also customizeable through traits with no slow down    template lt int    Is gt  struct IntVector  using Type   IntVector lt Is    gt       template lt typename T Vector  int I New gt  struct PushFront  template lt int    Is  int I New gt  struct PushFront lt IntVector lt Is    gt  I New gt    IntVector lt I New Is    gt      template lt int I Size  typename T Vector   IntVector lt  gt  gt  struct Iota   Iota lt  I Size-1  typename PushFront lt T Vector I Size-1 gt   Type gt      template lt typename T Vector gt  struct Iota lt 0 T Vector gt    T Vector     template lt char C In gt  struct ToUpperTraits       enum   value    C In  gt    a   amp  amp  C In  lt   z     C In -   a - A   C In        template lt typename T gt  struct TableToUpper  template lt int    Is gt  struct TableToUpper lt IntVector lt Is    gt  gt       static char at const char in           static const char table      ToUpperTraits lt Is gt   value              return table in             int tableToUpper const char c       using Table   TableToUpper lt typename Iota lt 256 gt   Type gt       return Table  at c       with use case   std  transform in begin   in end   out begin   tableToUpper     For an in depth  many page  decription of how it works allow me to shamelessly plug my blog  http   metaporky blogspot de 2014 07 part-4-generating-look-up-tables-at html

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Boost string algorithms   include  lt boost algorithm string hpp gt   include  lt string gt   std  string str    quot Hello World quot    boost  to upper str    std  string newstr   boost  to upper copy lt std  string gt   quot Hello World quot

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Based on Kyle the hacker s ----- gt  answer with my extras  Ubuntu In terminal List all locales locale -a Install all locales sudo apt-get install -y locales locales-all Compile main cpp   g   main cpp  Run compiled program     a out  Results Zo   Salda  a played in La maldici  n del padre Cardona         a      Chlo   Zo   Salda  a played in La maldici  n del padre Cardona         a      Chlo   ZO   SALDA  A PLAYED IN LA MALDICI  N DEL PADRE CARDONA          O     CHLO   ZO   SALDA  A PLAYED IN LA MALDICI  N DEL PADRE CARDONA          O     CHLO   zo   salda  a played in la maldici  n del padre cardona         a      chlo   zo   salda  a played in la maldici  n del padre cardona         a      chlo      Windows In cmd run VCVARS developer tools  quot C  Program Files  x86  Microsoft Visual Studio 2019 Community VC Auxiliary Build vcvars64 bat quot   Compile main cpp  gt  cl  EHa main cpp   D  quot  DEBUG quot   D  quot  CONSOLE quot   D  quot  UNICODE quot   D  quot UNICODE quot   std c  17   DYNAMICBASE  quot kernel32 lib quot   quot user32 lib quot   quot gdi32 lib quot   quot winspool lib quot   quot comdlg32 lib quot   quot advapi32 lib quot   quot shell32 lib quot   quot ole32 lib quot   quot oleaut32 lib quot   quot uuid lib quot   quot odbc32 lib quot   quot odbccp32 lib quot    MTd Compilador de optimizaci  n de C C   de Microsoft  R  versi  n 19 27 29111 para x64  C  Microsoft Corporation  Todos los derechos reservados   main cpp Microsoft  R  Incremental Linker Version 14 27 29111 0 Copyright  C  Microsoft Corporation   All rights reserved    out main exe main obj kernel32 lib user32 lib gdi32 lib winspool lib comdlg32 lib advapi32 lib shell32 lib ole32 lib oleaut32 lib uuid lib odbc32 lib odbccp32 lib  Run main exe  gt main exe Results Zo   Salda  a played in La maldici  n del padre Cardona         a      Chlo   Zo   Salda  a played in La maldici  n del padre Cardona         a      Chlo   ZO   SALDA  A PLAYED IN LA MALDICI  N DEL PADRE CARDONA          O     CHLO   ZO   SALDA  A PLAYED IN LA MALDICI  N DEL PADRE CARDONA          O     CHLO   zo   salda  a played in la maldici  n del padre cardona         a      chlo   zo   salda  a played in la maldici  n del padre cardona         a      chlo     The code - main cpp  This code was only tested on Windows x64 and Ubuntu Linux x64         Filename  c  Users x Cpp main cpp    Path  c  Users x Cpp    Filename   home x Cpp main cpp    Path   home x Cpp    Created Date  Saturday  October 17th 2020  10 43 31 pm    Author  Joma       No Copyright 2020        include  lt iostream gt   include  lt set gt   include  lt string gt   include  lt locale gt      WINDOWS  if   WIN32   include  lt Windows h gt   include  lt conio h gt   define WINDOWS PLATFORM 1  define DLLCALL STDCALL  define DLLIMPORT  declspec dllimport   define DLLEXPORT  declspec dllexport   define DLLPRIVATE  define NOMINMAX    EMSCRIPTEN  elif defined   EMSCRIPTEN     include  lt emscripten emscripten h gt   include  lt emscripten bind h gt   include  lt unistd h gt   include  lt termios h gt   define EMSCRIPTEN PLATFORM 1  define DLLCALL  define DLLIMPORT  define DLLEXPORT   attribute    visibility  quot default quot      define DLLPRIVATE   attribute    visibility  quot hidden quot         LINUX - Ubuntu  Fedora    Centos  Debian  RedHat  elif    LINUX        gnu linux        linux        linux    linux   define LINUX PLATFORM 1  include  lt unistd h gt   include  lt termios h gt   define DLLCALL CDECL  define DLLIMPORT  define DLLEXPORT   attribute    visibility  quot default quot      define DLLPRIVATE   attribute    visibility  quot hidden quot      define CoTaskMemAlloc p  malloc p   define CoTaskMemFree p  free p     ANDROID  elif    ANDROID      ANDROID   define ANDROID PLATFORM 1  define DLLCALL  define DLLIMPORT  define DLLEXPORT   attribute    visibility  quot default quot      define DLLPRIVATE   attribute    visibility  quot hidden quot        MACOS  elif defined   APPLE     include  lt unistd h gt   include  lt termios h gt   define DLLCALL  define DLLIMPORT  define DLLEXPORT   attribute    visibility  quot default quot      define DLLPRIVATE   attribute    visibility  quot hidden quot      include  quot TargetConditionals h quot   if TARGET OS IPHONE  amp  amp  TARGET IPHONE SIMULATOR  define IOS SIMULATOR PLATFORM 1  elif TARGET OS IPHONE  define IOS PLATFORM 1  elif TARGET OS MAC  define MACOS PLATFORM 1  else   endif   endif    typedef std  string String  typedef std  wstring WString    define EMPTY STRING u8 quot  quot s  define EMPTY WSTRING L quot  quot s  using namespace std  literals  string literals   class Strings   public      static String WideStringToString const WString amp  wstr                if  wstr empty                          return String                      size t pos          size t begin   0          String ret    if WINDOWS PLATFORM         int size          pos   wstr find static cast lt wchar t gt  0   begin           while  pos    WString  npos  amp  amp  begin  lt  wstr length                          WString segment   WString  amp wstr begin   pos - begin               size   WideCharToMultiByte CP UTF8  WC ERR INVALID CHARS   amp segment 0   segment size    NULL  0  NULL  NULL               String converted   String size  0               WideCharToMultiByte CP UTF8  WC ERR INVALID CHARS   amp segment 0   segment size     amp converted 0   converted size    NULL  NULL               ret append converted               ret append   0                 begin   pos   1              pos   wstr find static cast lt wchar t gt  0   begin                     if  begin  lt   wstr length                          WString segment   WString  amp wstr begin   wstr length   - begin               size   WideCharToMultiByte CP UTF8  WC ERR INVALID CHARS   amp segment 0   segment size    NULL  0  NULL  NULL               String converted   String size  0               WideCharToMultiByte CP UTF8  WC ERR INVALID CHARS   amp segment 0   segment size     amp converted 0   converted size    NULL  NULL               ret append converted              elif LINUX PLATFORM    MACOS PLATFORM    EMSCRIPTEN PLATFORM         size t size          pos   wstr find static cast lt wchar t gt  0   begin           while  pos    WString  npos  amp  amp  begin  lt  wstr length                          WString segment   WString  amp wstr begin   pos - begin               size   wcstombs nullptr  segment c str    0               String converted   String size  0               wcstombs  amp converted 0   segment c str    converted size                 ret append converted               ret append   0                 begin   pos   1              pos   wstr find static cast lt wchar t gt  0   begin                     if  begin  lt   wstr length                          WString segment   WString  amp wstr begin   wstr length   - begin               size   wcstombs nullptr  segment c str    0               String converted   String size  0               wcstombs  amp converted 0   segment c str    converted size                 ret append converted              else         static assert false   quot Unknown Platform quot     endif         return ret             static WString StringToWideString const String amp  str                if  str empty                          return WString                       size t pos          size t begin   0          WString ret   ifdef WINDOWS PLATFORM         int size   0          pos   str find static cast lt char gt  0   begin           while  pos    std  string  npos                std  string segment   std  string  amp str begin   pos - begin               std  wstring converted   std  wstring segment size     1  0               size   MultiByteToWideChar CP UTF8  MB ERR INVALID CHARS   amp segment 0   segment size     amp converted 0   converted length                 converted resize size               ret append converted               ret append   0                 begin   pos   1              pos   str find static cast lt char gt  0   begin                     if  begin  lt  str length                  std  string segment   std  string  amp str begin   str length   - begin               std  wstring converted   std  wstring segment size     1  0               size   MultiByteToWideChar CP UTF8  MB ERR INVALID CHARS  segment c str    segment size     amp converted 0   converted length                 converted resize size               ret append converted               elif LINUX PLATFORM    MACOS PLATFORM    EMSCRIPTEN PLATFORM         size t size          pos   str find static cast lt char gt  0   begin           while  pos    String  npos                        String segment   String  amp str begin   pos - begin               WString converted   WString segment size    0               size   mbstowcs  amp converted 0    amp segment 0   converted size                 converted resize size               ret append converted               ret append   0                 begin   pos   1              pos   str find static cast lt char gt  0   begin                     if  begin  lt  str length                          String segment   String  amp str begin   str length   - begin               WString converted   WString segment size    0               size   mbstowcs  amp converted 0    amp segment 0   converted size                 converted resize size               ret append converted              else         static assert false   quot Unknown Platform quot     endif         return ret              static WString ToUpper const WString amp  data                WString result   data          auto amp  f   std  use facet lt std  ctype lt wchar t gt  gt  std  locale              f toupper  amp result 0    amp result 0    result size             return result             static String  ToUpper const String amp  data                return WideStringToString ToUpper StringToWideString data                static WString ToLower const WString amp  data                WString result   data          auto amp  f   std  use facet lt std  ctype lt wchar t gt  gt  std  locale             f tolower  amp result 0    amp result 0    result size             return result             static String ToLower const String amp  data                return WideStringToString ToLower StringToWideString data                enum class ConsoleTextStyle       DEFAULT   0      BOLD   1      FAINT   2      ITALIC   3      UNDERLINE   4      SLOW BLINK   5      RAPID BLINK   6      REVERSE   7      enum class ConsoleForeground       DEFAULT   39      BLACK   30      DARK RED   31      DARK GREEN   32      DARK YELLOW   33      DARK BLUE   34      DARK MAGENTA   35      DARK CYAN   36      GRAY   37      DARK GRAY   90      RED   91      GREEN   92      YELLOW   93      BLUE   94      MAGENTA   95      CYAN   96      WHITE   97     enum class ConsoleBackground       DEFAULT   49      BLACK   40      DARK RED   41      DARK GREEN   42      DARK YELLOW   43      DARK BLUE   44      DARK MAGENTA   45      DARK CYAN   46      GRAY   47      DARK GRAY   100      RED   101      GREEN   102      YELLOW   103      BLUE   104      MAGENTA   105      CYAN   106      WHITE   107     class Console   private      static void EnableVirtualTermimalProcessing          if defined WINDOWS PLATFORM         HANDLE hOut   GetStdHandle STD OUTPUT HANDLE           DWORD dwMode   0          GetConsoleMode hOut   amp dwMode           if    dwMode  amp  ENABLE VIRTUAL TERMINAL PROCESSING                         dwMode    ENABLE VIRTUAL TERMINAL PROCESSING              SetConsoleMode hOut  dwMode              endif            static void ResetTerminalFormat                 std  cout  lt  lt  u8 quot  033 0m quot              static void SetVirtualTerminalFormat ConsoleForeground foreground  ConsoleBackground background  std  set lt ConsoleTextStyle gt  styles                String format   u8 quot  033  quot           format append std  to string static cast lt int gt  foreground             format append u8 quot   quot            format append std  to string static cast lt int gt  background             if  styles size    gt  0                        for  auto it   styles begin    it    styles end      it                                format append u8 quot   quot                    format append std  to string static cast lt int gt   it                                     format append u8 quot m quot            std  cout  lt  lt  format        public      static void Clear           ifdef WINDOWS PLATFORM         std  system u8 quot cls quot     elif LINUX PLATFORM    defined MACOS PLATFORM         std  system u8 quot clear quot     elif EMSCRIPTEN PLATFORM         emscripten  val  global    quot console quot   call lt void gt  u8 quot clear quot     else         static assert false   quot Unknown Platform quot     endif            static void Write const String amp  s  ConsoleForeground foreground   ConsoleForeground  DEFAULT  ConsoleBackground background   ConsoleBackground  DEFAULT  std  set lt ConsoleTextStyle gt  styles              ifndef EMSCRIPTEN PLATFORM         EnableVirtualTermimalProcessing            SetVirtualTerminalFormat foreground  background  styles    endif         String str   s   ifdef WINDOWS PLATFORM         WString unicode   Strings  StringToWideString str           WriteConsole GetStdHandle STD OUTPUT HANDLE   unicode c str    static cast lt DWORD gt  unicode length     nullptr  nullptr    elif defined LINUX PLATFORM    defined MACOS PLATFORM    EMSCRIPTEN PLATFORM         std  cout  lt  lt  str   else         static assert false   quot Unknown Platform quot     endif   ifndef EMSCRIPTEN PLATFORM         ResetTerminalFormat     endif            static void WriteLine const String amp  s  ConsoleForeground foreground   ConsoleForeground  DEFAULT  ConsoleBackground background   ConsoleBackground  DEFAULT  std  set lt ConsoleTextStyle gt  styles                     Write s  foreground  background  styles           std  cout  lt  lt  std  endl             static void Write const WString amp  s  ConsoleForeground foreground   ConsoleForeground  DEFAULT  ConsoleBackground background   ConsoleBackground  DEFAULT  std  set lt ConsoleTextStyle gt  styles              ifndef EMSCRIPTEN PLATFORM         EnableVirtualTermimalProcessing            SetVirtualTerminalFormat foreground  background  styles    endif         WString str   s    ifdef WINDOWS PLATFORM         WriteConsole GetStdHandle STD OUTPUT HANDLE   str c str    static cast lt DWORD gt  str length     nullptr  nullptr    elif LINUX PLATFORM    MACOS PLATFORM    EMSCRIPTEN PLATFORM         std  cout  lt  lt  Strings  WideStringToString str    else         static assert false   quot Unknown Platform quot     endif   ifndef EMSCRIPTEN PLATFORM         ResetTerminalFormat     endif            static void WriteLine const WString amp  s  ConsoleForeground foreground   ConsoleForeground  DEFAULT  ConsoleBackground background   ConsoleBackground  DEFAULT  std  set lt ConsoleTextStyle gt  styles                     Write s  foreground  background  styles           std  cout  lt  lt  std  endl             static void WriteLine                 std  cout  lt  lt  std  endl             static void Pause                 char c          do                       c   getchar                std  cout  lt  lt   quot Press Key  quot   lt  lt  std  endl            while  c    64           std  cout  lt  lt   quot KeyPressed quot   lt  lt  std  endl             static int PauseAny bool printWhenPressed   false  ConsoleForeground foreground   ConsoleForeground  DEFAULT  ConsoleBackground background   ConsoleBackground  DEFAULT  std  set lt ConsoleTextStyle gt  styles                     int ch   ifdef WINDOWS PLATFORM         ch    getch     elif LINUX PLATFORM    MACOS PLATFORM    EMSCRIPTEN PLATFORM         struct termios oldt  newt          tcgetattr STDIN FILENO   amp oldt           newt   oldt          newt c lflag  amp     ICANON   ECHO           tcsetattr STDIN FILENO  TCSANOW   amp newt           ch   getchar            tcsetattr STDIN FILENO  TCSANOW   amp oldt    else         static assert false   quot Unknown Platform quot     endif         if  printWhenPressed                        Console  Write String 1  ch   foreground  background  styles                     return ch              int main         std  locale  global std  locale u8 quot en US UTF-8 quot         String dataStr   u8 quot Zo   Salda  a played in La maldici  n del padre Cardona         a      Chlo   quot       WString dataWStr   L quot Zo   Salda  a played in La maldici  n del padre Cardona         a      Chlo   quot       std  string locale   u8 quot  quot         std  string locale   u8 quot de DE UTF-8 quot         std  string locale   u8 quot en US UTF-8 quot       Console  WriteLine dataStr       Console  WriteLine dataWStr       dataStr   Strings  ToUpper dataStr       dataWStr   Strings  ToUpper dataWStr       Console  WriteLine dataStr       Console  WriteLine dataWStr       dataStr   Strings  ToLower dataStr       dataWStr   Strings  ToLower dataWStr       Console  WriteLine dataStr       Console  WriteLine dataWStr                 Console  WriteLine u8 quot Press any key to exit quot s  ConsoleForeground  DARK GRAY       Console  PauseAny         return 0

User · Answer

This c   function always returns the upper case string      include  lt locale gt    include  lt string gt  using namespace std   string toUpper  string str       locale loc       string n       for  string  size type i 0  i lt str length      i          n    toupper str i   loc       return n

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Without using any libraries   std  string YourClass  Uppercase const std  string  amp  Text        std  string UppperCaseString      UppperCaseString reserve Text size         for  std  string  const iterator it Text begin    it lt Text end      it                UppperCaseString push back   0x60  lt   it   amp  amp    it  lt  0x7B       it - static cast lt char gt  0x20      it             return UppperCaseString

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try the toupper   function   include  lt ctype h gt    it accepts characters as arguments  strings are made up of characters  so you ll have to iterate over each individual character that when put together comprise the string

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Short solution using C  11 and toupper     for  auto  amp  c  str  c   toupper c

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ALL of these solutions on this page are harder than they need to be    Do this  RegName    SomE StRing That you wAnt ConvErTed   NameLength   RegName Size    for  int forLoop   0  forLoop  lt  NameLength    forLoop         RegName forLoop    tolower RegName forLoop        RegName is your string   Get your string size don t use string size   as your actual tester  very messy and  can cause issues  then  the most basic for loop     remember string size returns the delimiter too so use  lt  and not  lt   in your loop test   output will be  some string that you want converted

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string StringToUpper string strToConvert       for  std  string  iterator p   strToConvert begin    strToConvert end      p    p          p   toupper  p       return p      Or   string StringToUpper string strToConvert        std  transform strToConvert begin    strToConvert end    strToConvert begin      toupper        return strToConvert

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Using Boost Text  which will work for Unicode text  boost  text  text t    Hello World   boost  text  text uppered  boost  text  to title t  std  inserter uppered  uppered end      std  string newstr   uppered extract

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struct convert      void operator   char amp  c    c   toupper  unsigned char c                 string uc str  for each uc str begin    uc str end    convert      Note  A couple of problems with the top solution   21 5 Null-terminated sequence utilities The contents of these headers shall be the same as the Standard C Library headers  lt ctype h gt    lt wctype h gt    lt string h gt    lt wchar h gt   and  lt stdlib h gt          Which means that the cctype members may well be macros not suitable for direct consumption in standard algorithms   Another problem with the same example is that it does not cast the argument or verify that this is non-negative  this is especially dangerous for systems where plain char is signed   The reason being  if this is implemented as a macro it will probably use a lookup table and your argument indexes into that table  A negative index will give you UB

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If you only want to capitalize  try this function   include  lt iostream gt    using namespace std   string upper string text       string upperCase      for int it   text           if it gt 96 amp  amp it lt 123               upperCase    char it-32            else              upperCase    char it                       return upperCase     int main         string text    quot   abcdfghopqrvmwxyz    quot       cout lt  lt text lt  lt  quot   quot       text   upper text       cout lt  lt text      return 0      Error  Range-based  for  loops are not allowed in C  98 mode

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My solution  clearing 6th bit for alpha     include  lt ctype h gt   inline void toupper char  str        while  str i             if  islower str i                str i   amp    32     Clear bit 6 as it is what differs  32  between Upper and Lowercases         i

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works for ASCII -- no clear advantage over what is already posted     std  string toupper const std  string  amp  s        std  string ret s size    char         for unsigned int i   0  i  lt  s size      i          ret i     s i   lt    z   amp  amp  s i   gt    a     s i -  a - A     s i       return ret

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Do you have ASCII or International characters in strings    If it s the latter case   uppercasing  is not that simple  and it depends on the used alphabet  There are bicameral and unicameral alphabets  Only bicameral alphabets have different characters for upper and lower case  Also  there are composite characters  like Latin capital letter  DZ    u01F1  DZ   which use the so called title case  This means that only the first character  D  gets changed   I suggest you look into ICU  and difference between Simple and Full Case Mappings  This might help   http   userguide icu-project org transforms casemappings

[c++] Convert a String In C++ To Upper Case

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