C语言文件操作

#include <stdio.h>
FILE *fopen(const char *path,const char *mode)

#include <stdio.h>
int main(int argc, const char *argv[])
{
    if (NULL==fopen("testfile","r")) {
        printf("file open failed!\n");
    }else{
        printf("file open success!\n");
    }
    return 0;
}

r:只读方式，文件必须存在
w:只写方式，若文件存在，则原有内容会被清除；若文件不存在，则会建立文件
a:追加方式打开只写文件，只允许进行写操作，若文件存在，则添加的内容放在文件末尾；若不存在，则建立文件
+:可读可写
b:以二进制方式打开文件
t:以文本方式打开文件(默认方式下以文本方式打开文件)

#include <stdio.h>
int fclose(FILE *fp) 

#include <stdio.h>
size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);

#include <stdio.h>
int main(int argc, const char *argv[])
{
    /*
     * fp:file pointer
     * nmemb:number to read from file
     * numread:number successfully read from file
     */
    FILE *fp;
    int nmemb=5,numread;
    char list[nmemb+1];
    /*
     * open the file
     */
    if ((fp=fopen("text","rb"))==NULL) {
        printf("failed open file\n");
        exit(1);
    }
    /*
     * read file and close file
     */
    numread=(int)fread(list,sizeof(char),nmemb,fp);
    fclose(fp);
    /*
     * if numread bigger than nmemb,make list[numread]='\0',so we can safely printf the string
     */
    if(numread<=nmemb)
    {
        list[numread]='\0';
    }
    printf("%s\n",list);
    return 0;
}

size_t fwrite(const void *ptr, size_t size, size_t nmemb,FILE *stream);

#include <stdio.h>
int main(int argc, const char *argv[])
{
    FILE *fp;
    if ((fp=fopen("text","a"))==NULL) {
        printf("failed open file\n");
        exit(1);
    }
    fwrite("hello",sizeof(char),5,fp);
    return 0;
}

int fgetc(FILE *stream);
int fputc(int c, FILE *stream);

#include <stdio.h>
int main(int argc, const char *argv[])
{
    FILE *fp;
    int c;
    /*
     * open file.mode:w+.(read and write)
     */
    if ((fp=fopen("text","w+"))==NULL) {
        printf("failed open file\n");
        exit(1);
    }
    /*
     * read data from stdin
     */
    while ( (c=getchar())!=EOF) {
        fputc(c,fp);
    }
    /*
     * rewind file pointer to 0
     */
    rewind(fp);
    /*
     * read data from file to stdin
     */
    printf("Press some key to read the file");
    getchar();
    while ((c=fgetc(fp))!=EOF) {
        putchar(c);
    }
    return 0;
}

char *fgets(char *s, int size, FILE *stream);
int fputs(const char *s, FILE *stream);

fputs:成功时返回一个非负值,失败时返回EOF
fgets:成功返回指针s,失败返回NULL

#include <stdio.h>
int main(int argc, const char *argv[])
{
    FILE *fp;
    if ((fp=fopen("text","w+"))==NULL) {
            printf("failed open file\n");
            exit(1);
    }
    if(fputs("hello",fp)<0){
        printf("error.\n");
    }else{
        printf("success\n");
    }
    return 0;
}

#include <stdio.h>
#define SIZE 8
int main(int argc, const char *argv[])
{
    FILE *fp;
    char s[SIZE];
    if ((fp=fopen("text","r"))==NULL) {
        printf("failed open file\n");
        exit(1);
    }
    if (fgets(s,SIZE,fp)==NULL) {
        printf("fgets failed\n");
    }else{
        printf("%s",s);
    }
    return 0;
}

int feof(FILE *stream);

#include <stdio.h>
int main(int argc, const char *argv[])
{
    FILE *fp;
    int c;
    if ((fp=fopen("text","r"))==NULL) {
            printf("failed open file\n");
            exit(1);
    }
    do {
        c=fgetc(fp);
        if(c!=EOF)/*when fp point  to EOF,feof still is 0.but not 0 when read the next char*/
            putchar(c);
    } while (!feof(fp));
    fclose(fp);
    return 0;
}