pretty-format json file using lex

json-format.l

/* Lex program to pretty-format json file. ***WARNING-Amateurish*** */
%{
   int string=0;
   int gi=0;
   void indent(int i);
   int prev_close=0;
%}
%%

\\\" { //Matching an escaped double quote
  putc('\\',stdout);
  putc('"',stdout);
  prev_close=0;
};

\" { //Matching a double quote
  string=!string;
  putc(*yytext,stdout);
  prev_close=0;
};

[\{\[\(] { //Matching open type braces
  if(!string)
  {  
    if(prev_close)
    {
      putc('\n',stdout);
      indent(gi);
    }
    putc(*yytext,stdout);    
    putc('\n',stdout);
    gi++;
    indent(gi);
  }
  else
  {
    putc(*yytext,stdout);
  }
  prev_close=0;
};
    
[\}\]\)] { //Matching close type braces
  if(!string)
  {
    putc('\n',stdout);
    gi--;
    indent(gi);
    putc(*yytext,stdout);
  }
  else
  {
    putc(*yytext,stdout);
  }
  prev_close=1;
};

[,] { //Matching comma
  if(!string)
  {
    if(prev_close)
    {
      putc('\n',stdout);
      indent(gi);
    }
    putc(*yytext,stdout);
    putc('\n',stdout);
    indent(gi);
  }
  else
  {
    putc(*yytext,stdout);
  }
  prev_close=0;
};

[ \t] { //Matching whitespace
  if(!string)
  {
    //Eat up unwanted whitespace 
  }
  else
  {
    putc(*yytext,stdout);
    prev_close=0;
  }
};
[\n] { //Matching New line character
 //You're not allowed anywhere here. Die...
};
. { //Matching any other character
  if(prev_close)
  {
    putc('\n',stdout);
    indent(gi);
  }
  putc(*yytext,stdout);
  prev_close=0;
};
%%
void indent(int i)
{
   char c = ' '; //Whitespace character to be used for Indenting
   while(0<i--)
   {
      putc(c,stdout);
   }
}
int main(int argc, char **argv)
{
   FILE *fin,*fout;
   if(argc>1)
   {
      fin = fopen(argv[1],"r");
      if(!fin)
      {
         fprintf(stderr,"Could not open %s\n",argv[1]);
         exit(0);
      }
      yyin=fin;
   }
   if(argc>2)
   {
      fout = fopen(argv[2],"w");
      if(!fout)
      {
         fprintf(stderr,"Could not write to %s\n",argv[2]);
         exit(0);
      }
      stdout=fout;
   }
   if(argc>3)
   {
      fprintf(stderr,"Extra arguments are ignored.");
   }
   yylex();
   putc('\n',stdout);
   return 0;
}
int yywrap()
{
   return 1;
}