Converting a char array into an structure similar to int argc and char** argv

Question

I have read a text line from a file, and I need to convert it to an structure similar to main function arguments. For example if the char array is char* text="There are books in the library." and I have below structure definition:

struct mystruct{
   int argc;
   char** argv;
};

if I have struct mystruct a , with the function foo(a, text) I end up with a.argc equal to 6, a.argv[0] equal to There , a.argv[1] equal to are , ... .

Is there any function or library in CI can use for this purpose? Since this conversion is done automatically for input arguments when we execute C main function.

Answer 1

You could use strtok to do this split, like this:

struct split_result {
    int cnt;
    char *buf;
    char **strs;
};

int
split(const char *str, struct split_result *rst)
{
    int idx, str_num;
    char *buf, *sep, **strs;

    buf = strdup(str);
    if (buf == NULL) {
        perror("strdup");
        return -1;
    }

    str_num = 1;
    strs = malloc(str_num * sizeof(char *));
    if (strs == NULL) {
        perror("malloc");
        return -1;
    }

    sep = " \t";
    idx = 0;
    for (strs[idx] = strtok(buf, sep);
         strs[idx];
         strs[idx] = strtok(NULL, sep))
    {
        idx++;
        if (idx >= str_num) {
            str_num += 10;
            strs = realloc(strs, str_num * sizeof(char *));
            if (strs == NULL) {
                perror("realloc");
                return -1;
            }
        }
    }

    rst->cnt = idx;
    rst->strs = strs;
    rst->buf = buf;

    return 0;
}

---

Here is a test program and its output:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct split_result {
    int cnt;
    char *buf;
    char **strs;
};

int
split(const char *str, struct split_result *rst)
{
    int idx, str_num;
    char *buf, *sep, **strs;

    buf = strdup(str);
    if (buf == NULL) {
        perror("strdup");
        return -1;
    }

    str_num = 1;
    strs = malloc(str_num * sizeof(char *));
    if (strs == NULL) {
        perror("malloc");
        return -1;
    }

    sep = " \t";
    idx = 0;
    for (strs[idx] = strtok(buf, sep);
         strs[idx];
         strs[idx] = strtok(NULL, sep))
    {
        idx++;
        if (idx >= str_num) {
            str_num += 10;
            strs = realloc(strs, str_num * sizeof(char *));
            if (strs == NULL) {
                perror("realloc");
                return -1;
            }
        }
    }

    rst->cnt = idx;
    rst->strs = strs;
    rst->buf = buf;

    return 0;
}

int
main(void)
{
    int i, j;
    struct split_result rst;
    const char *msg[] = {
        "",
        " One",
        " One  Two",
        " One  Two Tree  ",
        "There are books in the library.",
        NULL,
    };

    for (i = 0; msg[i]; i++) {
        if (split(msg[i], &rst) < 0) {
            exit(EXIT_FAILURE);
        }

        printf("msg[%d] = >>%s<<\n", i, msg[i]);
        for (j = 0; j < rst.cnt; j++) {
            printf("cnt = %d: |%s|\n", j, rst.strs[j]);
        }

        free(rst.strs);
        free(rst.buf);
    }

    exit(EXIT_SUCCESS);
}

Output:

$ ./a.out 
msg[0] = >><<
msg[1] = >> One<<
cnt = 0: |One|
msg[2] = >> One  Two<<
cnt = 0: |One|
cnt = 1: |Two|
msg[3] = >> One  Two Tree  <<
cnt = 0: |One|
cnt = 1: |Two|
cnt = 2: |Tree|
msg[4] = >>There are books in the library.<<
cnt = 0: |There|
cnt = 1: |are|
cnt = 2: |books|
cnt = 3: |in|
cnt = 4: |the|
cnt = 5: |library.|

Answer 2

I presume the file have a number that specifies the number of arguments. if that is the case then create a loop and read each string until you encounter a delimiter ( again, assuming that you were told there is one ). If you don't have "the" number of arguments then add a member of type unsigned, in your struct, to keep track of the number of words read. You really don't need to create a split_function, but it doesn't hurt if you decided to create one :)