fgets讀取檔案時的注意事項

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1 文字檔 a.txt 內容如下

2 c代碼

  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");    }

輸出結果

　

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

總結: fgets讀取時,如果指定的讀取大小,小於實際行大小 那麼 不添加\n做結尾,使用\0 ,然後接著讀取沒讀完的當前行資料作為新的一行開始

　　  fgets讀取時,如果指定讀取大小.大於實際行大小,那麼將\n添加到末端.再添加\0

　　　\0不算做有效長度裡的元素,\n算有效長度裡元素

fgets讀取檔案時的注意事項