安全读取长度未知的字符串 [英] Safely reading in strings of unknown length
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问题描述
我正在尝试使用fgets安全地获取未知长度的字符串
I am trying to safely get in strings of unknown length with using fgets
到目前为止,这是我一直能想到的代码,但是现在我仍然坚持如何继续前进.
This is the code I have been able to come up with so far, but now I am stuck on how to conitinue forward.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#define DEFLEN 4
#define CHUNKSZ 2
int i = 0;
int size =0;
int size2 =0;
char* ln1;
char* ln2;
FILE *fpin;
char *getStrFromFile( FILE *fpins )/*file stream to read string from */
{
DEFLEN = malloc( CHUNKSZ *sizeof(int));
while(1){
if( fgets(ln1+size2, DEFLEN, fpin) == NULL) {
if(size > 0){
return (ln1);
}
else {
return (NULL);
free(ln1);
}
}
else{
size2=strlen(ln1);
if(ln1[size2 -1] == '\n'){
return (ln1);
}
else{
ln2=malloc(size+CHUNKSZ * sizeof(char));
assert(ln2);
strcpy(ln2, ln1);
free (ln1);
ln1 = ln2;
return (ln1);
}
}
}
我也收到DEFLEN = malloc行的错误
I also get an error for the DEFLEN = malloc line
错误:左值必须作为赋值的左操作数
error: lvalue required as left operand of assignment
推荐答案
预编译器将使用代码中的DEFINE.因此,您不能为定义分配任何内容!
A DEFINE in your code is used by the pre-compiler. So you cant assign anything to a define!
此行
DEFLEN = malloc( CHUNKSZ *sizeof(int));
被替换为
4 = malloc( CHUNKSZ *sizeof(int));
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