C语言 将文件的每一行读入数组
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Reading each line of file into array
提问by Celeritas
I'm reading a file and want to put each line into a string in an array. The length of the file is arbitrary and the length of each line is arbitrary (albeit assume it will be less than 100 characters).
我正在读取一个文件，并希望将每一行放入一个数组中的一个字符串中。文件的长度是任意的，每一行的长度是任意的（尽管假设它将少于 100 个字符）。
Here's what I've got and it's not compiling. Essentially this is an array to an array of characters, right? So shouldn't it be char** words = (**char)malloc(sizeof(*char));?
这是我所拥有的，它没有编译。本质上，这是一个字符数组的数组，对吗？所以不应该char** words = (**char)malloc(sizeof(*char));吗？
#include <stdio.h>
#include <stdlib.h>
int main(){
int BUFSIZE = 32767;//max number of lines to read
char** words = (**char)malloc(sizeof(*char));//gives error: expected expression before 'char'
FILE *fp = fopen("coll.txt", "r");
if (fp == 0){
fprintf(stderr, "Error opening file");
exit(1);
}
int i = 0;
words[i] = malloc(BUFSIZE);
while(fscanf(fp, "%100s", words[i]) == 1)//no line will be longer than 100
{
i++;
words[i] = realloc(words, sizeof(char*)*i);
}
int j;
for(j = 0; j < i; j++)
printf("%s\n", words);
return 0;
}
Note: I've read "Reading from a file and storing in array" but it doesn't answer my question.
注意：我读过“从文件中读取并存储在数组中”，但它没有回答我的问题。
回答by willus
There are a few issues with your program. The realloc() statement is not used correctly. I also prefer fgets() for getting a line. Here is my solution. This also uses realloc() to increase the allocation of the buffer lines so that you neither have to know the number of lines in advance nor do you have to read the file in two passes (faster that way). This is a common technique to use when you don't know how much memory you'll have to allocate in advance.
您的程序存在一些问题。realloc() 语句未正确使用。我也更喜欢 fgets() 来获取一行。这是我的解决方案。这也使用 realloc() 来增加缓冲区行的分配，这样您既不必提前知道行数，也不必分两遍读取文件（那样更快）。当您不知道必须提前分配多少内存时，这是一种常用的技术。
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int lines_allocated = 128;
int max_line_len = 100;
/* Allocate lines of text */
char **words = (char **)malloc(sizeof(char*)*lines_allocated);
if (words==NULL)
{
fprintf(stderr,"Out of memory (1).\n");
exit(1);
}
FILE *fp = fopen("coll.txt", "r");
if (fp == NULL)
{
fprintf(stderr,"Error opening file.\n");
exit(2);
}
int i;
for (i=0;1;i++)
{
int j;
/* Have we gone over our line allocation? */
if (i >= lines_allocated)
{
int new_size;
/* Double our allocation and re-allocate */
new_size = lines_allocated*2;
words = (char **)realloc(words,sizeof(char*)*new_size);
if (words==NULL)
{
fprintf(stderr,"Out of memory.\n");
exit(3);
}
lines_allocated = new_size;
}
/* Allocate space for the next line */
words[i] = malloc(max_line_len);
if (words[i]==NULL)
{
fprintf(stderr,"Out of memory (3).\n");
exit(4);
}
if (fgets(words[i],max_line_len-1,fp)==NULL)
break;
/* Get rid of CR or LF at end of line */
for (j=strlen(words[i])-1;j>=0 && (words[i][j]=='\n' || words[i][j]=='\r');j--)
;
words[i][j+1]='char** words = (**char)malloc(sizeof(*char));
';
}
/* Close file */
fclose(fp);
int j;
for(j = 0; j < i; j++)
printf("%s\n", words[j]);
/* Good practice to free memory */
for (;i>=0;i--)
free(words[i]);
free(words);
return 0;
}
回答by Cobain
You should change the line:
您应该更改该行：
char** words=(char **)malloc(sizeof(char *)*Max_Lines);
into this:
进入这个：
##代码##