C语言怎么做到从文件中读取一行数据,然后改变这一行内容 c语言如何从文件中读入一行数据
C\u8bed\u8a00\u600e\u4e48\u4fee\u6539txt\u6587\u4ef6\u4e2d\u7684\u4e00\u884c\u6570\u636e\u5173\u4e8e\u8fd9\u4e2a\u95ee\u9898\uff0c\u672c\u4eba\u4e5f\u6ca1\u6709\u4ec0\u4e48\u597d\u7684\u65b9\u6cd5\u3002
\u63d0\u4e2a\u5efa\u8bae\uff1a\u9996\u5148\u5c06\u540e100\u4e2a\u5b57\u7b26\u8bfb\u5165\u6570\u7ec4\uff0c\u5185\u5b58\u8bbf\u95ee\u80af\u5b9a\u6bd4\u6587\u4ef6\u8bbf\u95ee\u8981\u5feb
\u5c31\u662f\u8fd9\u5757\uff1a
do
{
fscanf(fp,"%c",&mm); //\u9010\u884c\u626b\u63cf
}
while(mm!='\n'); //\u5224\u65ad\u5012\u6570\u7b2c\u4e8c\u884c\u7684\u6362\u884c\u7b26
\u53e6\u5916\u82e5\u60f3\u6539\u8fdb\uff0c\u4e2a\u4eba\u611f\u89c9\u6587\u4ef6\u7684\u78c1\u76d8\u8bbf\u95ee\u672c\u8eab\u5c31\u5f88\u6162\uff0c\u53ef\u4ee5\u8003\u8651\u5728\u6587\u4ef6\u4e0d\u5927\u65f6\u76f4\u63a5\u7528\u4e00\u4e9b\u5185\u5b58\u64cd\u4f5c
\u5173\u952e\u6280\u5de7\uff1a
\u6bcf\u884c\u6570\u636e\u4e2a\u6570\u968f\u673a\uff0c\u53ef\u7528
c
=
fgetc(fin);
ungetc(c,fin);
\u68c0\u67e5\u662f\u5426\u8bfb\u5230
\u6362\u884c\u7b26\u6216\u6587\u4ef6\u7ed3\u675f\u7b26\u3002
\u4f8b\u5982\uff1a
a.txt
1
2
3
45
56
6
7
8
9
10
\u81f3\u4e8e\u8bb0\u5f55\u6bcf\u884c\u6570\u636e\u4e2a\u6570\uff0c\u5b58\u653e\u5230\u6570\u7ec4\uff0c\u7b49\u7b49\uff0c\u53ef\u4ee5\u81ea\u5df1\u8865\u5145\u5b8c\u5584\u3002
\u7a0b\u5e8f\uff1a
#include
int
main(
)
{
file
*fin;
int
a,c;
fin=fopen("a.txt","rw");
while(1){
c
=
fgetc(fin);
if
(c==eof)
break;
if
(c=='\n')
{printf("\n==========\n");
continue;};
ungetc(c,fin);
fscanf(fin,"%d",&a);
printf("%d
",a);
}
fclose(fin);
return
0;
}
1、用fgets函数可以读取文件中某行的数据，某列数据就必须一个一个读入每行的第几个字符，再存入到一个字符串当中。
2、例程：
#include<stdio.h>
#include<string.h>
void main()
{
char a[100],b[100],c[100];
int i=3,j=4,k=0; //第三行，第四列
FILE *fp = fopen("data.txt","r");
while(fgets(c,100,fp)){ //读入每行数据
i--;
if(i==0) strcpy(a,c); //读到第三行数据
b[k++]=c[j-1]; //把每行的那列字符拷到b中
}
b[k]=0;
printf("第%d行数据：%s
",i,a);
printf("第%d列数据：%s
",j,b);
fclose(fp);
}
楼主可以查一下fprintf, fscanf, fgetc, fgets, fread, fopen, fclose这些函数。前缀f表示的就是文件版本的输入输出函数（printf，scanf这些函数楼主想必知道吧？）
不懂可追问，祝楼主学习愉快。
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