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fgets读取文件时的注意事项

1 文本文件 a.txt 内容如下

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2 c代码
  FILE *fil;    if (!(fil = fopen("/home/rudy/projects/paser/a.txt", "rb"))) {        printf("File I/O error,the File is not exist\n");        exit(0);    } int line = 0;    while(!feof(fil)) {        if (fgetc(fil) == ‘\n‘) {            ++line;        }    }    ++line;    fclose(fil);    if (!(fil = fopen("/home/rudy/projects/paser/a.txt", "rb"))) {        printf("File I/O error,the File is not exist\n");        exit(0);    }    char ** all =(char **) malloc( line * sizeof(char *));    for (int iCurrLineIndex = 0; iCurrLineIndex < line; ++iCurrLineIndex) {        all[iCurrLineIndex] = (char *) malloc(20 );        fgets(all[iCurrLineIndex], 21, fil);    } for (int iCurrLineIndex = 0; iCurrLineIndex < line; ++iCurrLineIndex) {        printf("this is len = %d \n",strlen(all[iCurrLineIndex]));        for(int i = 0;i <11;i++) {            if (all[iCurrLineIndex][i] == ‘\0‘)            {                printf("%s\n ","this is 0");            }else if ( all[iCurrLineIndex][i]== ‘\n‘)            {                printf("%s\n ","this is n");            }else{                printf("%c ",all[iCurrLineIndex][i]);            }        }        printf("\n");    }

输出结果

 

this is len = 10 1 2 3 4 5 6 7 8 9 this is n this is 0 this is len = 10 a b c d e f g h i this is n this is 0 this is len = 9 1 2 3 4 5 6 7 8 9 this is 0 this is 0

总结: fgets读取时,如果指定的读取大小,小于实际行大小 那么 不添加\n做结尾,使用\0 ,然后接着读取没读完的当前行数据作为新的一行开始

    fgets读取时,如果指定读取大小.大于实际行大小,那么将\n添加到末端.再添加\0

   \0不算做有效长度里的元素,\n算有效长度里元素

fgets读取文件时的注意事项