C multiline string literal

Question

Is there any way to have multi-line plain-text  constant literals in C       la Perl  Maybe some parsing trick with  includeing a file  I can t think of one  but boy  that would be nice  I know it ll be in C  0x

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Option 1  Using boost library  you can declare the string as below  const boost  string view helpText    This is very long help text  n         Also more text is here n         And here n      Pass help text here setHelpText helpText     Option 2  If boost is not available in your project  you can use std  string view   in modern C

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define MULTILINE         VA ARGS   Consumes everything between the parentheses  Replaces any number of consecutive whitespace characters by a single space

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Since an ounce of experience is worth a ton of theory  I tried a little test program for MULTILINE    define MULTILINE         VA ARGS    const char  mstr           MULTILINE 1  2  3             1  2  3      MULTILINE 1 2 3               1 2 3      MULTILINE 1   2   3           1   2   3      MULTILINE  1   2   3          1   2   3      MULTILINE  1   2   3           1   2   3       MULTILINE 1               2               3                   1 2 3      MULTILINE 1 n2 n3 n           1 n2 n3 n      MULTILINE 1 n               2 n               3 n                 1 n 2 n 3 n      MULTILINE 1   2   3           1    2    3       Compile this fragment with cpp -P -std c  11 filename to reproduce   The trick behind    VA ARGS   is that   VA ARGS   does not process the comma separator  So you can pass it to the stringizing operator  Leading and trailing spaces are trimmed  and spaces  including newlines  between words are compressed to a single space then  Parentheses need to be balanced  I think these shortcomings explain why the designers of C  11  despite    VA ARGS    saw the need for raw string literals

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You can just do this   const char  text    This is my string it is         very long

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In C  11 you have raw string literals   Sort of like here-text in shells and script languages like Python and Perl and Ruby   const char   vogon poem   R V0G0N               O freddled gruntbuggly thy micturations are to me                  As plured gabbleblochits on a lurgid bee                Groop  I implore thee my foonting turlingdromes                And hooptiously drangle me with crinkly bindlewurdles  Or I will rend thee in the gobberwarts with my blurlecruncheon  see if I don t                    by Prostetnic Vogon Jeltz  see p  56 57   V0G0N     All the spaces and indentation and the newlines in the string are preserved   These can also be utf-8 16 32 or wchar t  with the usual prefixes    I should point out that the escape sequence  V0G0N  is not actually needed here   Its presence would allow putting    inside the string   In other words  I could have put                    by Prostetnic Vogon Jeltz  see p  56 57      note extra quotes  and the string above would still be correct   Otherwise I could just as well have used  const char   vogon poem   R             The parens just inside the quotes are still needed

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C  11   std  string index html R html   lt  DOCTYPE html gt   lt html lang  en  gt   lt head gt       lt meta charset  UTF-8  gt       lt title gt VIPSDK MONITOR lt  title gt       lt meta http-equiv  refresh  content  10  gt   lt  head gt   lt style type  text css  gt   lt  style gt   lt  html gt   html

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Well     Sort of  The easiest is to just use the fact that adjacent string literals are concatenated by the compiler   const char  text      This text is pretty long  but will be      concatenated into just a single string       The disadvantage is that you have to quote      each part  and newlines must be literal as      usual      The indentation doesn t matter  since it s not inside the quotes   You can also do this  as long as you take care to escape the embedded newline  Failure to do so  like my first answer did  will not compile    const char  text2      Here  on the other hand  I ve gone crazy   and really let the literal span several lines    without bothering with quoting each line s   content  This works  but you can t indent      Again  note those backslashes at the end of each line  they must be immediately before the line ends  they are escaping the newline in the source  so that everything acts as if the newline wasn t there  You don t get newlines in the string at the locations where you had backslashes  With this form  you obviously can t indent the text since the indentation would then become part of the string  garbling it with random spaces

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A probably convenient way to enter multi-line strings is by using macro s  This only works if quotes and parentheses are balanced and it does not contain  top level  comma s    define MULTI LINE STRING a   a const char  text   MULTI LINE STRING    Using this trick    you don t need to use quotes    Though newlines and     multiple     white   spaces   will be replaced by a single whitespace     printf     s   n  text     Compiled with gcc 4 6 or g   4 6  this produces    Using this trick    you don t need to use quotes  Though newlines and multiple white spaces will be replaced by a single whitespace     Note that the   cannot be in the string  unless it is contained within parenthesis or quotes  Single quotes is possible  but creates compiler warnings   Edit  As mentioned in the comments   define MULTI LINE STRING         VA ARGS   allows the use of

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Just to elucidate a bit on  emsr s comment in  unwind s answer  if one is not fortunate enough to have a C  11 compiler  say GCC 4 2 1   and one wants to embed the newlines in the string  either char   or class string   one can write something like this   const char  text      This text is pretty long  but will be n     concatenated into just a single string  n     The disadvantage is that you have to quote n     each part  and newlines must be literal as n     usual      Very obvious  true  but  emsr s short comment didn t jump out at me when I read this the first time  so I had to discover this for myself   Hopefully  I ve saved someone else a few minutes

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You can also do this   const char  longString   R      This is  a very  long  string

[c++] C++ multiline string literal

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