Read from file and use read parts to call functions

Question

I have a file that contains calls to functions present in my code. Some examples of functions are criar(), inserir(elemento, conjunto), listar(conjunto) where the arguments are integers passed to the function. These functions must be called through the arquivo.txt that will contain, for example:

criar() inserir(1,0) listar(0)

To read the file, I used the following function:

void leArquivo(){
FILE *arq;

    if((arq = fopen("arquivo.txt", "r")) == NULL)
            printf("Erro ao abrir o arquivo.\n");

    char buffer[100];
    char *p;

    while (fscanf (arq, "%s\n", buffer) != EOF) {
            p = buffer;
            printf("%s\n", p);    
    }    
    fclose (arq);
}

However, this only prints the "name" of the function itself, and does not call it. For example, if in the file the function is criar(), he printa criar() and not the return of the create function. I found that, as printf("%d", criar()); returns the function value, printf("%d\n", p); would return the same, but not.

I thought I’d use the function strcmp() to be able to compare if the names are equal and hence call the function, and I succeeded in functions without arguments, but I do not know how to do for functions like inserir(elemento, conjunto), where it is not possible to "predict" the arguments. Any suggestions on how to call these functions from reading the file?

Answer 1

See if the function below fits your need:

this code snippet will read the text file and look for the function in a structure already defined and execute the command if it exists.

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

#include <readline/readline.h>
#include <readline/history.h>

typedef void cmd_function_t(char *);

//estrutura dos comandos
typedef struct {
    char *name;
    cmd_function_t *func;
} command_t;

static void execute_command(char *line);
static command_t *find_command(char *name);

//comandos para rodar
static void comando1(char *arg);
static void comando2(char *arg);
static void comando3(char *arg);
static void comando4(char *arg);

command_t commands[] = {
        { "comando1", comando1 },
        { "comando2", comando2 },
        { "comando3", comando3 },
        { "comando4", comando4 },
};

static command_t *find_command(char *name) {
    register int i;
    size_t namelen;

    if ((name == NULL) || (*name == '\0'))
        return ((command_t *) NULL);

    namelen = strlen(name);
    for (i = 0; commands[i].name; i++) {
        if (strncmp(name, commands[i].name, namelen - 1) == 0) {
            /* make sure the match is unique */
            if ((commands[i + 1].name)
                    && (strncmp(name, commands[i + 1].name, namelen) == 0))
                return ((command_t *) NULL);
            else
                return (&commands[i]);
        }
    }

    return ((command_t *) NULL);
}

//função que pega o texto encontrado e executa
static void execute_command(char *line) {

    register int i;
    command_t *command;
    char *word;

    /* Isolate the command word. */
    i = 0;
    while (line[i] && whitespace(line[i]))
        i++;
    word = line + i;

    while (line[i] && !whitespace(line[i]))
        i++;

    if (line[i])
        line[i++] = '\0';

    command = find_command(word);

    if (!command) {
        return;
    }

    /* Get argument to command, if any. */
    while (whitespace(line[i]))
        i++;

    word = line + i;

    /* invoke the command function. */
    (*command->func)(word);
}

static void comando1(char *arg) {

    printf("\nExecutando o Comando 1\n");
    fflush(NULL);
}

static void comando2(char *arg) {

    printf("\nExecutando o Comando 2\n");
    fflush(NULL);
}

static void comando3(char *arg) {

    printf("\nExecutando o Comando 3\n");
    fflush(NULL);
}

static void comando4(char *arg) {

    printf("\nExecutando o Comando 4\n");
    fflush(NULL);
}

int main(int argc, char **argv) {

    FILE * fp;
    char * line = NULL;
    size_t len = 0;
    ssize_t read;
    char *cmd;

    fp = fopen("arquivo.txt", "r");
    if (fp == NULL)
        exit(EXIT_FAILURE);

    if ((read = getline(&line, &len, fp)) != -1) {
        if (line == NULL) {
            printf("Sem comando\n");
        }

        cmd = line;

        if (*cmd) {
            execute_command(cmd);
        }

    }

    fclose(fp);
    if (line)
        free(line);
    exit(EXIT_SUCCESS);

}