include <stdio.h>
#include <string.h>
int main(void)
{
    FILE *ap,*bp;
    char name[10],ch[40];
    gets(name);
    ap = fopen(name,"r");
    bp = fopen("xx.txt","a+");
    while(fgets(ch,40,ap) != NULL)
    {
        printf("读取文件成功\n");
        if((strcmp(ch,"163")) == 0)
        {
            printf("比较成功\n");
            fputs(ch,bp);
        }
        else
            printf("比较失败\n");
    }
    fclose(ap);
    fclose(bp);
    return 0;
}

这里我想把文件一行一行的读入数组,再比较数组中是否有163如果有就把它写入另一个文件,
为什么比较不出来呢?

The result stored in string is appended with a null character.

The newline character, if read, is included in the string.

MSDN的解释。
试试看        if((strcmp(ch,"163\n")) == 0)

不要直接用strcmp，自己写一个吧

" border="0" />

#include <stdio.h>
#include <string.h>
int main(void)
{
    FILE *ap,*bp;
    char ch[40];
    char name[10]="2.txt";
    ap = fopen(name,"r");//从2.txt中读取内容
    bp = fopen("1.txt","a+");
    while(fgets(ch,40,ap) != NULL)
    {
        printf("读取文件成功\n");
        if((strcmp(ch,"163")) == 0)
        {
            printf("比较成功\n");
            fputs(ch,bp);//输出到1.txt中
        }
        else
            printf("比较失败\n");
    }
    fclose(ap);
    fclose(bp);
    return 0;
}//帮你改了

输出结果：
读取文件成功
比较成功

哦 对了 2.txt中内容务必是163