[ C ] парсинг строки

char* get_qs_param(char *param){
        FNAME();
        char *tok, *val, *par, *str, *str0 = NULL, *ret = NULL;
        if(!qs && !get_qs()) return NULL;
        str = str0 = strdup(qs);
        tok = strtok(str, "& \n");
        do{
                if(strcasecmp(tok, param)==0){
                        ret = strdup(" "); // переменная есть, значения нет
                        break;
                }
                if((val = strchr(tok, '=')) == NULL) continue;
                *val++ = '\0';
                par = tok;
                if(strcasecmp(par, param)==0){
                        if(strlen(val) > 0)
                                ret = strdup(val);
                        else
                                ret = strdup(" "); // переменная есть, значения нет
                        break;
                }
        }while((tok = strtok(NULL, "& \n"))!=NULL);
        free(str0);
        return ret;
}

char val[256];
int i;

sscanf(line, "param_%d=\"%255[^\"]\";", &i, val);

str[strlen(str) - 1] = '\0';

[      Matches a nonempty sequence of characters from the specified set of accepted characters; the
       next pointer must be a pointer to char, and there must be enough room for all the characters
       in the string, plus a terminating null byte.  The usual skip of leading white space is  sup‐
       pressed.  The string is to be made up of characters in (or not in) a particular set; the set
       is defined by the characters between the open bracket [ character  and  a  close  bracket  ]
       character.   The set excludes those characters if the first character after the open bracket
       is a circumflex (^).  To include a close bracket in the set, make  it  the  first  character
       after  the  open bracket or the circumflex; any other position will end the set.  The hyphen
       character - is also special; when placed between two other characters, it adds all interven‐
       ing characters to the set.  To include a hyphen, make it the last character before the final
       close bracket.  For instance, [^]0-9-] means the set "everything except close bracket,  zero
       through  nine,  and  hyphen".  The string ends with the appearance of a character not in the
       (or, with a circumflex, in) set or when the field width runs out.

s      Matches a sequence of non-white-space characters […] The input string stops at white space or at
       the maximum field width, whichever occurs first.

sscanf(line, "params_%d=\"%255[^\"]\";", &i, val);

$ cat test.c 
#include <stdio.h>

int main() {
    const char *line = "param_1=\"10000\";\n";

    char buf[256];
    int i;

    sscanf(line, "param_%d=\"%255[^\"]\";", &i, buf);

    printf("i=%d\n", i);
    printf("val=«%s»\n", buf);

    return 0;
}

$ cc test.c 
$ ./a.out
i=1
val=«10000»
$ _

const char *line = "param_1=\"10000\"; param_2=\"2000\"; param_100= \"4000\"  ;param_999 =\"  3.2" ";

#include <stdio.h>

int main() {
    const char *line = "hello=\"world\";\n";

    char key[256];
    char val[256];

    sscanf(line, "%255[^=]=\"%255[^\"]\";", key, val);

    printf("key=«%s»\n", key);
    printf("val=«%s»\n", val);

    return 0;
}

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <regex.h>
#include <string.h>
char *expr="([a-zA-Z_][a-zA-Z0-9]*)[[:space:]]*=[[:space:]]*\"([^\"]*)\"";
char buffer[1024];
int main() {
    regex_t reg;
    regmatch_t match[3];
    char *str;
    if (regcomp(&reg,expr,REG_EXTENDED|REG_ICASE)!=0) {
        exit(EXIT_FAILURE);
    }
    while(!feof(stdin)) {
        str=fgets(buffer,1024,stdin);
        if (str==NULL)
            continue;
        str+=strspn(str," \t\v");
        if (str[0]=='\0' || str[0]=='\n' || str[0]=='#')
            continue;
        if (regexec(&reg,str,3,match,0)!=0) {
            fprintf(stderr,"Error in string:%s",str);
            continue;
        }
        printf("variable=%.*s\n",match[1].rm_eo-match[1].rm_so,str+match[1].rm_so);
        printf("value=%.*s\n",match[2].rm_eo-match[2].rm_so,str+match[2].rm_so);
    }
    regfree(&reg);
    return 0;
}

#include <stdio.h>

int main() {
    char line[1024], key[256], val[256];

    while (fgets(line, sizeof line, stdin))
        if (sscanf(line, "%255[^=]=\"%255[^\"]\";", key, val) == 2)
            printf("key=«%s»\nval=«%s»\n", key, val);

    return 0;
}

$ cat input_test.txt

params_1="value1";
params_2="value2";
params_3="value3";
params_4="value4";
params_5="value5";
params_6="value6";
params_7="value7";
params_8="value8";
params_9="value9";
params_10="value10";


$ cat test1.l

%{
    int idx;
%}

%x left
%x right

%%

^params_    BEGIN(left);
<left>=\"   BEGIN(right);

<left>[0-9]+      {idx = atoi(yytext); } 

<right>([^\"]+)   {BEGIN(INITIAL);
                    /* add here malloc and strcpy */
                   printf("%d = %s\n", idx, yytext);}

\n                {BEGIN(INITIAL);}

.    { }

%%

main()
{
  yylex();
}


$ flex test1.l
$ gcc -O2 -o test1 lex.yy.c -lfl
$ ./test1 < input_test.txt

1 = value1
2 = value2
3 = value3
4 = value4
5 = value5
6 = value6
7 = value7
8 = value8
9 = value9
10 = value10