p2-7.c

来自「UNIX程序设计教程」· C语言 代码 · 共 48 行

#include <stdio.h>
#include <stdlib.h>
char buf[132];
int main(int argc, char *argv[])
{
    FILE *fd;
    fpos_t pos;
    if (argc !=2){
        fprintf(stderr,"Usage: %s mode\n",argv[0]);
        exit(EXIT_FAILURE);
    }
    /* 打开一个文件 */
    if(argv[1][0]!='a'){
        /* 打开该文件写数据*/
        if ((fd = fopen("test_file","w+")) == NULL){
            perror("fopen faild");
            exit(EXIT_FAILURE);
        }
    }
    else{
        /* 打开该文件添加数据*/
        if ((fd = fopen("test_file","a+")) == NULL){
            perror("fopen faild");
            exit(EXIT_FAILURE);
        }
    }
    /* 写入二行数据 */
    fputs("0123456789",fd);
    fputs("ABCDEFGHIJ",fd);
    /* 查看当前文件尾位置 */
    fseek(fd,0,SEEK_END);
    fgetpos(fd,&pos);
    printf("current file end position is %ld\n",pos);
    /* 定位至文件尾之后30字节 */
    fseek(fd,30,SEEK_END);
    /* 查看当前文件尾位置 */
    fgetpos(fd,&pos);
    printf("Now we call fseek(fd,30,SEEK_END)\n");
    printf("current file position is %ld\n",pos);
    /* 写入数据 */
    fputs("abcdefg",fd);
    printf("Now we write %c%s%c\n",'\"',"abcdefg",'\"');
    /* 查看当前文件尾位置 */
    fgetpos(fd,&pos);
    printf("current position of file end is %ld\n",pos);
    fclose(fd);
}