Char指针 - 如何赋予价值？ [英] Char pointer - How to give value?

问题描述

我刚刚开始学习C并且正在研究指针，但是我很难对以下内容感到困难：


如果我有一个结构，包括一个指向char的指针（在我的情况下，我已经将b $ b命名为文件名），在主代码中，我想使用那个指针

来创建一个内存位置并分配一个字符串。


我在主代码中得到了以下内容（structPtr是一个指针

到他们创建的结构类型）：

structPtr-> filename = malloc（10 * sizeof（char））;

如何给出一个值，让逗号保持字符串值为cust.txt。到这个

字段？


非常感谢任何帮助，


谢谢，

Alij

Hi,

I have just started learning C and am working on pointers but am
having difficulty with the following:

If i have a struct, that includes a pointer to char (in my case, i''ve
named it filename), and in the main code, I want to use that pointer
to create a memory location and assign a character string.

I have gotten the following in the main code (structPtr is a pointer
to they type of struct i have created):

structPtr->filename = malloc(10 * sizeof(char));

How do I give a value, lets stay string value of "cust.txt" to this
field?

Will appreciate any help,

Thanks,

Alij

推荐答案

3月19日下午6:49，alij < aliasger.jaf ... @ gmail.comwrote：

On Mar 19, 6:49 pm, "alij" <[e-mail]:

我刚开始学习C和我正在研究指针，但是我很难用以下内容：


如果我有一个结构，它包含一个指向char的指针（在我的情况下，我'$

将其命名为filename），在主代码中，我想使用该指针

来创建一个内存位置并分配一个字符串。


我在主代码中得到了以下内容（structPtr是一个指针

到他们创建的结构类型）：


structPtr-> filename = malloc（10 * sizeof（char））;


如何给出一个值，让逗号保持字符串值为cust.txt到这个

字段？

Hi,

I have just started learning C and am working on pointers but am
having difficulty with the following:

If i have a struct, that includes a pointer to char (in my case, i''ve
named it filename), and in the main code, I want to use that pointer
to create a memory location and assign a character string.

I have gotten the following in the main code (structPtr is a pointer
to they type of struct i have created):

structPtr->filename = malloc(10 * sizeof(char));

How do I give a value, lets stay string value of "cust.txt" to this
field?

strcpy（structPtr-> filename，" cust.txt"）;


顺便说一下，sizeof（ char）总是1，所以malloc（10）会这样做。

strcpy(structPtr->filename,"cust.txt");

By the way, sizeof(char) is always 1, so malloc(10) will do.

感谢任何帮助，


谢谢，


Alij

Will appreciate any help,

Thanks,

Alij

3月19日下午1:58，Francine.Ne ...... @ googlemail.com写道：

On Mar 19, 1:58 pm, [e-mail] wrote:

3月19日下午6:49，alij < aliasger.jaf ... @ gmail.comwrote：

On Mar 19, 6:49 pm, "alij" <[e-mail]:

您好，

Hi,

我刚刚开始学习C并正在研究指针，但是我很难用以下内容：

I have just started learning C and am working on pointers but am
having difficulty with the following:

如果我有一个结构，包括一个指向char的指针（在我的情况下，我已经将b $ b命名为文件名），在主代码中，我想使用那个指针

用于创建内存位置并分配字符串。

If i have a struct, that includes a pointer to char (in my case, i''ve
named it filename), and in the main code, I want to use that pointer
to create a memory location and assign a character string.

我在主代码中得到以下内容（structPtr是一个指针

到他们创建的结构类型）：

I have gotten the following in the main code (structPtr is a pointer
to they type of struct i have created):

structPtr-> filename = malloc（10 * sizeof（char））;

structPtr->filename = malloc(10 * sizeof(char));

如何给出一个值，让逗号保持字符串值为cust.txt到这个

字段？

How do I give a value, lets stay string value of "cust.txt" to this
field?

strcpy（structPtr-> filename，" cust.txt"）;


顺便说一下，sizeof（ char）总是1，所以malloc（10）会这样做。

strcpy(structPtr->filename,"cust.txt");

By the way, sizeof(char) is always 1, so malloc(10) will do.

感谢任何帮助，

Will appreciate any help,

谢谢，

Thanks,

Alij

Alij

谢谢为了你的帮助!!

Thank you for your help!!

alij写道：

alij wrote:

我刚刚开始学习C并且正在研究指针，但是我很难用以下方法：


如果我有一个struct，包括指向char的指针（在我的情况下，我已经将b $ b命名为文件名），在主代码中，我想使用那个指针

创建一个内存位置并分配一个字符串。


我在主代码中得到了以下内容（structPtr是一个指针

到他们创建的结构类型）：

structPtr-> filename = malloc（10 * sizeof（char））;

Hi,

I have just started learning C and am working on pointers but am
having difficulty with the following:

If i have a struct, that includes a pointer to char (in my case, i''ve
named it filename), and in the main code, I want to use that pointer
to create a memory location and assign a character string.

I have gotten the following in the main code (structPtr is a pointer
to they type of struct i have created):

structPtr->filename = malloc(10 * sizeof(char));

^^^^^^^^^^^^^^

sizeof（char）的定义是1。以上是打字练习到最后。

^^^^^^^^^^^^^^
sizeof(char) is 1 by definition. The above is typing practice to no end.

>

我如何给出一个值，让逗号保持字符串值为cust.txt到这个

字段？

>
How do I give a value, lets stay string value of "cust.txt" to this
field?

#include< stdio.h>

#include< stdlib.h>

#include < string.h>


#define FIELDSIZE 10

#define FILENAME" cust.txt"


struct foo

{

char * filename;

};


int main（void ）

{

struct foo thething，* structPtr =& thething;


if（！（structPtr-> filename） = malloc（FIELDSIZE）））{

printf（" malloc failed。我退出！\ n）;

退出（EXIT_FAILURE）;

}

if（strlen（FILENAME）> = FIELDSIZE）{

printf（" \"" FILENAME" \"）太长了。我退出了！\ n;

免费（structPtr->文件名）;

退出（EXIT_FAILURE）;

}

strcpy（structPtr-> filename，FILENAME）;

printf（" structPtr-> filename is \"％s \" \ n"

∧ andthing .filename是\"％s \" \ n"，

structPtr-> filename，thething.filename）;

free（structPtr-> ; filename）;

返回0;

}

structPtr-> filename是cust.txt

和thething.filename是cust.txt

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

#define FIELDSIZE 10
#define FILENAME "cust.txt"

struct foo
{
char *filename;
};

int main(void)
{
struct foo thething, *structPtr = &thething;

if (!(structPtr->filename = malloc(FIELDSIZE))) {
printf("malloc failed. I quit!\n");
exit(EXIT_FAILURE);
}
if (strlen(FILENAME) >= FIELDSIZE) {
printf("\"" FILENAME "\" is too long. I quit!\n");
free(structPtr->filename);
exit(EXIT_FAILURE);
}
strcpy(structPtr->filename, FILENAME);
printf("structPtr->filename is \"%s\"\n"
" and thething.filename is \"%s\"\n",
structPtr->filename, thething.filename);
free(structPtr->filename);
return 0;
}
structPtr->filename is "cust.txt"
and thething.filename is "cust.txt"

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