爲什麼我的數組的前一個元素髮生了變化（C中的字符串數組）

Question

我正在構建一個shell歷史函數以接收字符串並在程序運行時將其添加到字符串數組中。

我的問題是，無論何時我用一個新行（字符串）更新數組緩存中的前一個元素將被我的CWD（當前工作目錄）填充，但我需要保留先前設置的字符串。

這是我的主循環得到的字符串，並試圖以存儲與高速緩存功能的歷史：

//prints out the cwd; then loops to take in the line, split it up into arguments, and attempt to execute it 
//while lsh_execute returns 0, then frees up the allocated space 
void lsh_loop(void) 
{ 
    char *line;    //pointer to a char (the beg. of an array of chars) 
    char *cache[10] = {NULL};  //history array 
    char **args;    //pointer to a pointer of a char... 
    int status, counter = 0, i, j; 

    do { 
    printf("%s>", getcwd(0,0));  //print cwd 
    line = lsh_read_line();  //call read line 
    counter = lsh_cache_line(counter,line, cache); 
    printf("This is counter:%i\n", counter);   

    for(i=0; i<10; i++){ 
     printf("This is cache[%i]:%s\n", i, cache[i]); 
    } 

    args = lsh_split_line(line); //split line 
    status = lsh_execute(args);  //execute the split args 

    free(line);    //free memory 
    free(args); 
    } while (status);   //continue as long as execute returns 1 

} 

在這個函數中，我複製輸入字符串行字符串數組：

int lsh_cache_line(int counter,char *line, char *cache[10]){ 

    (cache[counter]) = line; 
    printf("This is cache[%i]:%s\n", counter, cache[counter]); 
    counter++; 
    counter = counter % 10; 
    return counter; 

} 

這是我的程序的輸出：

paul@paul-VirtualBox:~/Desktop$ gcc shell.c 
paul@paul-VirtualBox:~/Desktop$ ./a.out 
/home/paul/Desktop>HI 
This is cache[0]:HI 
This is counter:1 
This is cache[0]:HI 
This is cache[1]:(null) 
This is cache[2]:(null) 
This is cache[3]:(null) 
This is cache[4]:(null) 
This is cache[5]:(null) 
This is cache[6]:(null) 
This is cache[7]:(null) 
This is cache[8]:(null) 
This is cache[9]:(null) 
lsh: No such file or directory 
/home/paul/Desktop>this is my problem 
This is cache[1]:this is my problem 
This is counter:2 
This is cache[0]:/home/paul/Desktop 
This is cache[1]:this is my problem 
This is cache[2]:(null) 
This is cache[3]:(null) 
This is cache[4]:(null) 
This is cache[5]:(null) 
This is cache[6]:(null) 
This is cache[7]:(null) 
This is cache[8]:(null) 
This is cache[9]:(null) 
lsh: No such file or directory 
/home/paul/Desktop>it overwrites my previous string with the cwd 
This is cache[2]:it overwrites my previous string with the cwd 
This is counter:3 
This is cache[0]:/home/paul/Desktop 
This is cache[1]:/home/paul/Desktop 
This is cache[2]:it overwrites my previous string with the cwd 
This is cache[3]:(null) 
This is cache[4]:(null) 
This is cache[5]:(null) 
This is cache[6]:(null) 
This is cache[7]:(null) 
This is cache[8]:(null) 
This is cache[9]:(null) 
lsh: No such file or directory 
/home/paul/Desktop>^C 
paul@paul-VirtualBox:~/Desktop$ 

我已經嘗試用不同的方式來聲明和初始化字符串數組，但是這種方式似乎工作得最好。

我在做什麼錯？

Answer 1

cache中沒有字符串存儲。

類似於strdup會創建存儲空間，但稍後需要free內存。

int lsh_cache_line(int counter,char *line, char *cache[10]){ 

(cache[counter]) = strdup(line); 
printf("This is cache[%i]:%s\n", counter, cache[counter]); 
counter++; 
counter = counter % 10; 
return counter; 

} 

有10個字符串插槽，但沒有字符串值的內存。你需要分配一些內存。

Answer 2

我敢打賭，你的lsh_read_line（）函數總是返回不同文本的相同緩衝區。然後將指向此緩衝區的指針存儲到數組中的不同單元格中。一旦將它放入行變量中，您應該將文本複製到新分配的字符串中，並且以後只能使用此新副本進行工作。