what chars are special in c? - c

Question

Hey guys so I have this text with special chars in it and I wold like to "escape" special chars to be able to compile my program but I do not know are / : - = special chars ? And do I need to escape them as well ? Here is example
static const char *postthis="text and spec chars";
and here is example of text which I want to put in
<text:Text
text:text="http://text.text.text/text/text/"
text:text="text:text:text-text-text">
<text:Text>
<text text="http://text.com/text">
<productID>20630175</textID>
</text>
</text:text>
</text:text>
So I put \ before < and " but again I got error, what do I need to escape and how ?
static const char *postthis="\<text:Text
text:text=\"http://text.text.text/text/text/\"
text:text=\"text:text:text-text-text\"\>
\<text:Text\>
\<text text="http://text.com/text\"\>
\<textID\>20630175\</textID\>
\</text\>
\</text:text\>
\</text:text\>";

Answer 1

I think you need to escape the end of the line in a multiple line initializer
and the quotes. If there were tabs or new-lines you would need to escape those too \t \n.
static const char *postthis="\<text:Text\
text:text=\"http://text.text.text/text/text/\"\n\
text:text=\"text:text:text-text-text\">\n\
<text:Text>\n\
<text text="http://text.com/text\"\>\n\
<textID>20630175</textID>\n\
</text>\n\
</text:text>\n\
</text:text>";

Answer 2

The only characters you need to escape inside of a C string are \, and ". There's no reason to quote <. Newlines can be escaped, or you can include them as \n (which I prefer, since it lets you indent more nicely IMO). You cannot simply embed unquoted newlines, however (which is probably your main problem).
XML supports both ' and " as quotation, so you can almost always simplify your life by using '.
static const char *postthis=
"<text:Text\n"
" text:text='http://text.text.text/text/text/'\n"
" text:text='text:text:text-text-text'>\n"
" <text:Text>\n"
" <text text='http://text.com/text'>\n"
" <productID>20630175</textID>\n"
" </text>\n"
" </text:text>\n"
"</text:text>";
Of course XML does not need the newlines, so you could just drop them unless you want this to be human-read.
Note that the above uses a multi-part C string. (Multiple "..." that are joined together.) I can't remember what version of C added that (or if it's a GNU extension). If you can't use it, then you can just escape the newlines:
static const char *postthis=
"<text:Text\
text:text='http://text.text.text/text/text/'\
...
</text:text>";
But it makes the indentation a little harder to customize without making your code look worse.

Answer 3

You time is much better spent putting that text in to a file and reading that. Hand editing XML is guaranteed to backfire.
If you are working an an iOS project you'd be able to use the NSString initialiser:
- (id)initWithContentsOfFile:(NSString *)path usedEncoding:(NSStringEncoding *)enc error:(NSError **)error
Or if you are using vanilla C something along the lines of
#include <stdio.h>
#define BUFF_SIZE 1024
int main(int argc, char **argv) {
char s[BUFF_SIZE];
FILE *fp = fopen( "file.xml", "r" );
int i = 0;
while ( !feof(fp) && i < BUFF_SIZE-1 ) {
s[i++] = fgetc(fp);
}
s[i]='\0';
printf("My string is here %s\n", s);
}

Answer 4

See http://en.cppreference.com/w/cpp/language/escape for all escape sequences in a string literal. These will need to be escaped if you want them unchanged. Any new lines you want in your string will need to be written as \n.
As already mentioned earlier, you could keep the text in a file and read it at run time.
If you have a lot of text you want to compile into your program, another easy solution is to use objcopy:
objcopy -I binary -O elf64-x86-64 -B i386 --rename-section .data=.rodata,alloc,load,readonly,data,contents your_text.txt your_text.o
This will give you a object file with the following symbols in it:
_binary_your_text_txt_start
_binary_your_text_txt_end
_binary_your_text_txt_size
Link against your_text.o and use the symbols to access the text. For example:
#include <stdio.h>
extern char _binary_your_text_txt_start;
extern char _binary_your_text_txt_end;
extern char _binary_your_text_txt_size;
int main(int argc, char *argv[])
{
const char * b = &_binary_your_text_txt_start;
const char * e = &_binary_your_text_txt_end;
size_t s = (size_t)&_binary_your_text_txt_size;
fwrite(b, s, 1, stdout);
return 0;
}