c - 不完整的 C 递归函数。我不知道如何正确实现

Question

我需要用C实现一个可以模拟pstree的递归函数，即将下面的数字想象成一个过程:

1 (father)
   2 (child of 1)
   3 (child of 1)
     4 (son of 3)
       5 (child of 4)
     6 (child of 3)

等等....

void imprime_Pstree(int i, int ntabs)
{
    int k = 0, j = 0, quantProc = 0;
    int procAtual;

    // Prints the number of tabs
    for(k = 0; k < ntabs; k++)
        printf("\t");

    quantProc = preenche_vetor(i);

    // Prints the process name
    imprimeNomeProcesso(i);


    for(j = 0; j < quantProc; j++) {

        imprime_Pstree(processos[j], ntabs+1);
    }

}

但它只打印父级(称为递归函数)和子级，没有其他子级。 我知道前一个子项的父项中缺少对递归函数的另一次调用，但是如何呢？

<小时/>

完整代码:

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

int processos[1000];

void limpa_vetor() {
    int i;
    for(i = 0; i < 1000; i++)
        processos[i] = 0;
}

int preenche_vetor(int proc) {
    char path[50];
    char string[100];
    int i, j = 0, cont = 0;
    char temp;
    FILE *arq;

    limpa_vetor();

    sprintf(path, "/proc/%d/task/%d/children", proc, proc);
    arq = fopen(path, "r");

    if (arq != NULL)
    {
        limpa_vetor();

        fscanf(arq, "%s", string);
        while(strcmp(string, "") != 0)
        {
            if(feof(arq)) break;
            processos[j] = atoi(string);
            cont++;

            fscanf(arq, "%c", &temp);
            fscanf(arq, "%s", string);
            j++;
        }
    }
    return cont;
}

void imprimeNomeProcesso(int proc) {
    char path[50];
    char string[100];
    int i, j = 0;
    char temp;
    FILE *arq;

    sprintf(path, "/proc/%d/stat", proc);
    arq = fopen(path, "r");

    if (arq != NULL)
    {
        fscanf(arq, "%s", string);
        while(strcmp(string, "") != 0)
        {
            if(feof(arq)) break;

            if(j == 1)
            {
                printf("%s ", string);
                break;
            }

            fscanf(arq, "%c", &temp);
            fscanf(arq, "%s", string);
            j++;
        }
        printf("\n");
    }

}

void imprime_Pstree(int i, int ntabs)
{
    int k = 0, j = 0, quantProc = 0;
    int procAtual;

    // Imprime a quantidade de tabs
    for(k = 0; k < ntabs; k++)
        printf("\t");

    quantProc = preenche_vetor(i);

    // Imprime o nome do processo
    imprimeNomeProcesso(i);


    for(j = 0; j < quantProc; j++) {

        imprime_Pstree(processos[j], ntabs+1);
    }

}

int main()
{
    imprime_Pstree(1, 0);

    return 0;
}

Answer 1

processos 是一个全局变量，包含 i 的所有子节点的列表。这在递归函数中不起作用。递归调用将覆盖数组。您必须将其设为本地变量并将其传递给必须分配值的函数:

void imprime_Pstree(int i, int ntabs)
{
    int k = 0, j = 0, quantProc = 0;
    int procAtual;
    int processos[1000];    // <-- have a local array

    // Imprime a quantidade de tabs
    for(k = 0; k < ntabs; k++)
        printf("\t");

    // pass that array to preenche_vetor()
    quantProc = preenche_vetor(i, processos );

   // Imprime o nome do processo
   imprimeNomeProcesso(i);


   for(j = 0; j < quantProc; j++) {

        imprime_Pstree(processos[j], ntabs+1);
   }   

}

当然，您还必须更改 preenche_vetor() 的签名，并且必须在那里进行初始化()。

编辑 正如 @Aconcagua ha 建议的那样，最好先确定 child 的数量，然后声明并填写 VLA