函数

strncpy()

  • 作用
    限制最大字符复制字符串，要比strcpy()更安全
  1. 参数
    (字符串指针，被复制的字符串指针，最大个数)

示例

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#include<stdio.h>
#include<stdlib.h>//提供exit()原型
#include<string.h>//提供strcpy(),strcat()原型
#define LEN 40
char * s_gets(char * st, int n);
int main(int argc, char *argv[])
{
    char name[LEN];
    char file[LEN];
    char ch;
    int ct = 0;
    FILE *in;
    FILE *out;

    printf("Please enter file name:");
    s_gets(name, LEN);//会将换行符替换为'\0'
    if((in = fopen(name, "r")) == NULL)
    {
        fprintf(stderr, "Could not open %s file", name);
        exit(EXIT_FAILURE);
    }
    strncpy(file, name, LEN);//限制字符串不超过40
    file[LEN - 4] = '\0';//超过40就截断
    strcat(file, ".io");
    if((out = fopen(file, "w")) == NULL)
    {
        fprintf(stderr, "Could not create output file");
        exit(EXIT_FAILURE);
    }
    while((ch = getc(in)) != EOF)
    {
        ct++;
        if(ct % 3 == 0)
            putc(ch, out);
    }
    if(fclose(out) != 0 || fclose(in) != 0)
        fprintf(stderr, "Error in closing file");

    return 0;
}
char * s_gets(char * st, int n)
{
    char * find;
    char * ret_val;

    ret_val = fgets(st, n, stdin);
    if (ret_val)
    {
        find = strchr(st, '\n');	//查找换行符
        if (find)
            *find = '\0';			//替换为空字符
        else
            while (getchar() != '\n')
                continue;			//处理多余输入
    }

    return ret_val;
}