This program, "ip4dec", converts lists of IPv4 addresses to decimal and prints t...

This program, "ip4dec", converts lists of IPv4 addresses to decimal and prints them as unsigned integers. Wrote this while experimenting with storing domain->ip mappings in a trie, such as https://github.com/tlwg/libdatrie

Name borrowed from https://github.com/ian-hamlin/ipdec

Note the trietool "list" command prints data as decimal not unsigned integer.

   sed -n 's/   //;wip4dec.l' << eof
    /* 
       not a domain name or ip address validator 
       input file format:
       (left-justified, no leading spaces)
       example.com 93.184.216.34 
       example.net 93.184.216.34 comment
    */
    int fileno(FILE *);
    int setenv(const char*,const char*,int);
    int unsetenv(const char*);
    #define echo do{if(fwrite(yytext,(size_t)yyleng,1,yyout)){}}while(0)
    #define jmp (yy_start) = 1 + 2 *
    int x=0,y=0,o=0;
   xa [0-9]{1,3}\x2e
   xb [0-9]{1,3}
   xc [0-9]{4,5} 
   xd ^[A-Za-z0-9\.-]+
   xe ^[^A-Za-z0-9]
   %s xa 
   %option noyywrap nounput noinput
   %%
   {xd} if(yytext[0]=='-'||yytext[0]=='.')jmp 0;else{o=0;y=0;x=0;setenv("x",yytext,1);jmp xa;}
   {xe} jmp 0;
   <xa>{xc} jmp 0;
   <xa>{xa}|{xb} {
    switch(o){
     case 0: y=atoi(yytext);if(y<1)break;x=y*16777216;y=0;o++;break;
     case 1: y=atoi(yytext);if(y>255)break;x=x+y*65536;y=0;o++;break;
     case 2: y=atoi(yytext);if(y>255)break;x=x+y*256;y=0;o++;break;
     case 3: y=atoi(yytext);if(y>255)break;x=x+y;printf("%s\t%u\n",getenv("x"),x);unsetenv("x");break;
     default: break;
     }
    }
   .|\n
   %%
   int main(){ yylex();exit(0) ;}

   eof

   flex -8iCrf ip4dec.l
   cc  -std=c89 -Wall -pedantic -I. -pipe lex.yy.c -static -o ip4dec

usage: ip4dec < input-file