阅读文件...... [英] Reading a file...

问题描述

大家好，我不是C的新手，但是我已经超过5年才使用它了...


我正试图读取一个有两倍的文本文件：


1.0 1.1 1.2 1.3 1.4

2.0 2.1 2.2 2.3 2.4

我'这样做（这只是试图达到目标的一个考验......）：


#include< stdio.h>

#include< stdlib.h>


int main（）{

FILE * pFile;

long lSize;

double * buffer;


pFile = fopen（" fichero_test.txt"，" r"）;

if（pFile == NULL）退出（1）;


//获取文件大小。

fseek（pFile，0，SEEK_END）;

lSize = ftell（pFile）;

倒带（pFile）;


//分配内存以包含整个文件。

buffer =（double *）malloc（lSize）;

if（buffer == NULL）exit（2）;


//复制文件进入缓冲区。

fread（缓冲区，1，lSize，pFile）;

printf（" Pos 2 - ％lf \ n"，buffer [2]）;

printf（" Pos 2 - ％lf \ n"，buffer [sizeof（double）* 2]）;


//终止

fclose（pFile）;

免费（缓冲）;

返回0;

}


输出结果为：


Pos 2 - 0.000000

Pos 2 - 0.000000


我做错了什么？，我可以将整个文件读入一个缓冲区？

Hi all, I''m not a newbie with C, but I don''t use it since more than 5 years...

I''m trying to read a text file which has doubles in it:

1.0 1.1 1.2 1.3 1.4
2.0 2.1 2.2 2.3 2.4
I''m doing this (it''s only a test trying to achieve the goal...):

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

int main () {
FILE* pFile;
long lSize;
double* buffer;

pFile = fopen ( "fichero_test.txt" , "r" );
if (pFile==NULL) exit (1);

// obtain file size.
fseek (pFile , 0 , SEEK_END);
lSize = ftell (pFile);
rewind (pFile);

// allocate memory to contain the whole file.
buffer = (double*) malloc (lSize);
if (buffer == NULL) exit (2);

// copy the file into the buffer.
fread (buffer,1,lSize,pFile);
printf("Pos 2 - %lf\n", buffer[2]);
printf("Pos 2 - %lf\n", buffer[sizeof(double)*2]);

// terminate
fclose (pFile);
free (buffer);
return 0;
}

The output is:

Pos 2 - 0.000000
Pos 2 - 0.000000

What am I doing wrong?, Can I read the whole file into a buffer?

推荐答案

EdUarDo写道：

EdUarDo wrote:

大家好，我是不是C的新手，但我从不使用它超过5年...


你对C i / o的工作方式有一些严重的误解。我推荐

你给自己写了一本好书（例如K& R），它会清楚地解释一下

。

我正试图读取一个有两倍的文本文件：

1.0 1.1 1.2 1.3 1.4
2.0 2.1 2.2 2.3 2.4


说实话，最简单的方法类似于： -


void read_line（double dd [5]，FILE * f）

{

if（fscanf （f，％lf％lf％lf％lf％lf，& dd [0]，& dd [1]，& dd [2]，

& dd [ 3]，& dd [4]

！= 5）

{

退出（EXIT_FAILURE）;

}

}


代码未经测试，未编译等。

我这样做（它只是试图达到目标的测试......）：
#include< stdlib.h>

int main （）{


int main（无效）


是更好的风格

FILE * pFile;
long lSize;
double * buffer;

pFile = fop en（fichero_test.txt; ，r ）;
if（pFile == NULL）exit（1）;


错误检查，好！


//获取文件大小。
fseek（pFile，0，SEEK_END）;
lSize = ftell（pFile）;
倒带（pFile）;


我不确定这是否适用于文本文件...


//分配内存以包含整个文件。
buffer =（double *）malloc（lSize）;


不要施放malloc（）

if（buffer == NULL）exit（2）;

//将文件复制到缓冲区。
fread（缓冲区，1，lSize，pFile）;
printf（Pos 2 - ％lf \ n，缓冲区[2]）;


所以你已经读了大约40个字符到一个缓冲区。你为什么期望在缓冲区中找到并加倍
？在ascii中，这就像


31 2E 30 20 31 2E 31等


（是的我知道它不会必须是ascii，但我认为这比''''更好地点了

。'''''''''''''''''''''''''''''' 1''''。''''1''等你不同意？）


你不能把字符填充到一个缓冲区中，并期待理智的结果。

printf（" Pos 2 - ％lf \ n"，buffer [sizeof（double）* 2]）;
//终止
fclose（pFile）;
免费（缓冲）;
返回0;
}

输出为：

Pos 2 - 0.000000
Pos 2 - 0.000000

我做错了什么？，我可以将整个文件读入缓冲区吗？

Hi all, I''m not a newbie with C, but I don''t use it since more than 5 years...
you have some severe misconceptions about how C i/o works. I recomend
you get yourself a good book (eg K&R) which will explain things
clearly.
I''m trying to read a text file which has doubles in it:

1.0 1.1 1.2 1.3 1.4
2.0 2.1 2.2 2.3 2.4
to be honest the simplest method is something like:-

void read_line (double dd [5], FILE *f)
{
if (fscanf(f, "%lf %lf %lf %lf %lf", &dd[0], &dd[1], &dd[2],
&dd[3], &dd[4)
!= 5)
{
exit (EXIT_FAILURE);
}
}

code is untested, uncompiled etc.
I''m doing this (it''s only a test trying to achieve the goal...):

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

int main () {
int main (void)

is better style
FILE* pFile;
long lSize;
double* buffer;

pFile = fopen ( "fichero_test.txt" , "r" );
if (pFile==NULL) exit (1);
error checking, good!

// obtain file size.
fseek (pFile , 0 , SEEK_END);
lSize = ftell (pFile);
rewind (pFile);
I''m not certain this works on a text file...

// allocate memory to contain the whole file.
buffer = (double*) malloc (lSize);
don''t cast malloc()
if (buffer == NULL) exit (2);

// copy the file into the buffer.
fread (buffer,1,lSize,pFile);
printf("Pos 2 - %lf\n", buffer[2]);
so you''ve read about 40 characters into a buffer. Why do you expect to
find and doubles in the buffer? In ascii that''s something like

31 2E 30 20 31 2E 31 etc.

(yes I know it doesn''t have to be ascii but I thought this made the
point
better than ''1'' ''.'' ''0'' '' '' ''1'' ''.'' ''1'' etc. you disagree?)

You can''t jsut stuff characters into a buffer and expect sane results.
printf("Pos 2 - %lf\n", buffer[sizeof(double)*2]);
// terminate
fclose (pFile);
free (buffer);
return 0;
}

The output is:

Pos 2 - 0.000000
Pos 2 - 0.000000

What am I doing wrong?, Can I read the whole file into a buffer?

是的，但你必须从字符转换为双。最好的

组合是fgets（）读取一行，然后是sscanf（）来解析

行。

总是检查返回值of sscanf（）。


-

Nick Keighley

yes, but you have to convert from characters to double. The best
combination is fgets() to read a line followed by sscanf() to parse the
line.
Always check the return value of sscanf().

--
Nick Keighley

>你对C i / o的运作方式有一些严重的误解。我推荐

> you have some severe misconceptions about how C i/o works. I recomend

你给自己写了一本好书（例如K& R），它会清楚地解释一些事情。


当然，现在我已经习惯了其他语言，而且我不记得任何关于CI / O的事情

you get yourself a good book (eg K&R) which will explain things
clearly.
Sure, now I''m used to other languages and indeed I don''t remember anything about C I/O

1.0 1.1 1.2 1.3 1.4
2.0 2.1 2.2 2.3 2.4

1.0 1.1 1.2 1.3 1.4
2.0 2.1 2.2 2.3 2.4

void read_line（double dd [5]，FILE * f）
{
if（fscanf（f，"％lf％lf％lf％lf％lf"，& dd [0]，& dd [1]，& dd [2]，
& ; dd [3]，& dd [4]
！= 5）
{
退出（EXIT_FAILURE）;
}
}

void read_line (double dd [5], FILE *f)
{
if (fscanf(f, "%lf %lf %lf %lf %lf", &dd[0], &dd[1], &dd[2],
&dd[3], &dd[4)
!= 5)
{
exit (EXIT_FAILURE);
}
}

好​​吧，它对我不起作用，因为真实文件每行可以有5,6或1000个项目。

Well, it doesn''t works for me because the real file could have 5, 6 or 1000 items per line.

//获取文件大小。
fseek（pFile，0，SEEK_END）;
lSize = ftell（pFile）;
倒带（pFile）;

// obtain file size.
fseek (pFile , 0 , SEEK_END);
lSize = ftell (pFile);
rewind (pFile);

我不确定这是否适用于文本文件...

I''m not certain this works on a text file...

确实...

It does...

//分配内存以包含整个文件。
buffer =（double *）malloc（lSize）;

不要投射malloc（）

// allocate memory to contain the whole file.
buffer = (double*) malloc (lSize);

don''t cast malloc()

ok

你不能把字符填充到一个缓冲区中，并期待理智的结果。


是的，我想是的，但我不确定，这就是我要求帮助的原因....

是的，但你必须从字符转换为double。最好的组合是fgets（）读取一行，然后是sscanf（）来解析
行。


我认为没有readLine函数，所以我需要阅读，直到我达到''\ n''字符，不是吗？ br />
总是检查sscanf（）的返回值。

ok
You can''t jsut stuff characters into a buffer and expect sane results.
Yeah, I guess that, but I wasn''t sure of it, that''s the reason I''ve asked for help....
yes, but you have to convert from characters to double. The best
combination is fgets() to read a line followed by sscanf() to parse the
line.
I suppose there isn''t a readLine function, so I''ll need to read until I reach a ''\n'' character, isn''t it?
Always check the return value of sscanf().

EdUarDo写道：

EdUarDo wrote:

大家好，我不是C的新手，但我已经超过5年没用过了......
我正在尝试阅读一个有文字的文件双打其中：

1.0 1.1 1.2 1.3 1.4
2.0 2.1 2.2 2.3 2.4

我这样做（这只是一次尝试实现目标...）：

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

int main（）{
FILE * pFile;
long lSize;
double * buffer;

pFile = fopen（" fichero_test.txt"，" r"）;
if（pFile == NULL）退出（1）;

//获取文件大小。
fseek（pFile，0，SEEK_END）;
lSize = ftell（pFile） ;
倒带（pFile）;

//分配内存以包含整个文件。
buffer =（double *）malloc（lSize）;
if（buffer == NULL）退出（2）;

//将文件复制到缓冲区。
fread（buffer，1，lSize，pFile）;
printf（" Pos 2 - ％lf \\ \\ n \\ n，缓冲区[2]）;
printf（Pos 2 - ％lf \ n，缓冲区[sizeof（double）* 2]）;

//终止
fclose（pFile）;
免费（缓冲）;
返回0;


输出结果为：

Pos 2 - 0.000000
Pos 2 - 0.000000

我做错了什么？，我可以将整个文件读入缓冲区吗？

Hi all, I''m not a newbie with C, but I don''t use it since more than 5
years...
I''m trying to read a text file which has doubles in it:

1.0 1.1 1.2 1.3 1.4
2.0 2.1 2.2 2.3 2.4
I''m doing this (it''s only a test trying to achieve the goal...):

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

int main () {
FILE* pFile;
long lSize;
double* buffer;

pFile = fopen ( "fichero_test.txt" , "r" );
if (pFile==NULL) exit (1);

// obtain file size.
fseek (pFile , 0 , SEEK_END);
lSize = ftell (pFile);
rewind (pFile);

// allocate memory to contain the whole file.
buffer = (double*) malloc (lSize);
if (buffer == NULL) exit (2);

// copy the file into the buffer.
fread (buffer,1,lSize,pFile);
printf("Pos 2 - %lf\n", buffer[2]);
printf("Pos 2 - %lf\n", buffer[sizeof(double)*2]);

// terminate
fclose (pFile);
free (buffer);
return 0;
}

The output is:

Pos 2 - 0.000000
Pos 2 - 0.000000

What am I doing wrong?, Can I read the whole file into a buffer?

这个帖子在''c file reading''帮助吗？

http://groups.google.com/group/comp=\"41f9f1ba8ac3d9

-

===== =========

不是学生

==============

Does this thread on ''c file reading'' help?

http://groups.google.com/group/comp....41f9f1ba8ac3d9
--
==============
Not a pedant
==============

这篇关于阅读文件......的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！