爲什麼文本寫入我的文件完美的罰款，直到最後幾行，當它在c循環？

Question

我一直在用c編寫一個小程序，正在創建的文件是正確的，直到最後150行左右，它開始獲取隨機字符，有時與我的程序的文件路徑或它的一部分寫入它。

注意：我使用mac視網膜和Xcode編寫和測試。

編輯：除非你想看到整個功能我已經把所給我的麻煩下面這段代碼

int vieditor() 
{ 
    FILE *readtext, *writetext,*testfile,*writeagain; 
    char mytest[1000][81],controller = '\0',worq;; 
    int x,charactersperline = 0,lines = 0,i,k; 



    /* this just creates a file with 1000 lines */ 
    testfile = fopen("/Users/scottcarlson/Classes/CS_222/test.txt","w"); 
    for (i = 0; i<1010; i = i+1) 
    { 
    fprintf(testfile,"this is line %d \n",i); 
    } 
    fclose(testfile); 
    /* end of file creation */ 

    readtext = fopen("/Users/scottcarlson/Classes/CS_222/test.txt","r"); 
    writetext = fopen("/Users/scottcarlson/Classes/CS_222/test1.txt","w"); 

    if (!readtext) 
    { 
     printf ("test.txt does not exist"); 
    } 
    else 
    { 
     while ((x = fgetc(readtext)) != EOF) 
     { 
      if (charactersperline < 80 && lines < 1000) 
      { 
       fprintf(writetext,"%c",x); 
       char ch = x; 
       mytest[lines][charactersperline] = ch; 
       if (lines < 20) 
       { 
        printf("%s",&mytest[lines][charactersperline]); 
       } 
      } 

      if (x != 10) 
      { 
       charactersperline += 1; 
      } 
      else 
      { 
       charactersperline = 0; 
       lines += 1; 
      } 

     } 
     fclose(readtext); 
     fclose(writetext); 


    } 
    do 
    { 
     fseek(stdin,0,SEEK_END); 
     system("stty raw -echo"); 
     controller = getchar(); 
     system("stty cooked echo"); 
    } 
    while (controller != 58); 
    scanf("%s",&worq); 
    if (worq == 'w') 
    { 
      writeagain = fopen("/Users/scottcarlson/Classes/CS_222/test.txt","w"); 
      for (k = 0; k<lines; k = k+1) 
      { 
        fprintf(writeagain,"%s",mytest[k]); 

      } 

    } 
    else if (strncmp(&worq,"q!",5)) 
    { 
     return 0; 
    } 


    return 0; 
} 

這是整個功能的一部分，但你並不需要看那個除非你想，那是害我麻煩的部分是底部就在這裏

do 
{ 
    fseek(stdin,0,SEEK_END); 
    system("stty raw -echo"); 
    controller = getchar(); 
    system("stty cooked echo"); 
} 
while (controller != 58); 
scanf("%s",&worq); 
if (worq == 'w') 
{ 
     writeagain = fopen("/Users/scottcarlson/Classes/CS_222/test.txt","w"); 
     for (k = 0; k<lines; k = k+1) 
     { 
       fprintf(writeagain,"%s",mytest[k]); 

     } 

} 
else if (strncmp(&worq,"q!",5)) 
{ 
    return 0; 
} 


return 0 

這應該打印（覆蓋）文件test.txt，其中它完美的罰款高達約840行，據我所知，根本沒有意義。

如果任何人都可以提供幫助，將不勝感激，因爲我無法在其他任何地方找到這方面的信息。

這裏是test.txt文件的一部分，它開始寫隨機事物。

this is line 838 
this is line 839 
∆ø_ˇthis is line 840 
¿_ˇthis is line 841 
this is line 842 
ˇthis is line 843 
this is line 844 
this is line 845 
this is line 846 
this is line 847 
’ø_ˇthis is line 848 
–è7zthis is line 849 
_ˇthis is line 850 
ˇthis is line 851 
this is line 852 
this is line 853 
this is line 854 
Ä◊ø_ˇthis is line 855 
◊ø_ˇthis is line 856 
ïˇthis is line 857 
_ˇthis is line 858 
this is line 859 
this is line 860 
this is line 861 
this is line 862 
∞Ãø_ˇthis is line 863 
Ãø_ˇthis is line 864 
éìˇthis is line 865 
this is line 866 
ˇthis is line 867 
/lithis is line 868 
this is line 869 
this is line 870 
p¶√_ˇthis is line 871 
de/DerivedData/Project_5.c-akilnssybkcyvuetuwkrqlyxxtie/Build/Pthis is line 872 
ystem_pthread.dylibthis is line 872 
ystem_pthread.dylibthis is line 873 
this is line 874 
ˇthis is line 875 
this is line 876 
this is line 877 
this is line 878 
this is line 879 
.c-akilnssythis is line 880 
this is line 881 
_ˇthis is line 882 

Answer 1

你不是null-terminating你的行mytest。當使用％s打印時，fprintf希望在字符串末尾看到'\ 0'。

將字符逐個字符複製到mytest中時，您需要將代碼添加到每行末尾的'\ 0'，或者您可以在開始時將整個數組初始化爲'\ 0'。 最簡單（但並非最有效）的方法是在每次添加字符後添加'\ 0'。

mytest[lines][charactersperline] = ch; 
mytest[lines][charactersperline+1] = '\0'; 

您還可以在該行的開始，當你開始一個新行添加一個零字節，因爲你的循環可能不會繼續圍繞把任何東西到該行。

注意，也有一個問題，如果你沒有在文件中有什麼，或者如果你的文件不以「\ n」結束，因爲你不會增加行數線

而且

printf("%s",&mytest[lines][charactersperline]); 

應該％C而不是％S作爲要打印一個字符。

Answer 2

scanf("%s",&worq); 

它看起來像worq是char。 "%s"轉換說明符將匹配字符串，並在提供的地址（單個字符的地址）中寫入字符串中的所有字符。

我懷疑你有緩衝區溢出的問題（即使只讀了1個字符，scanf將在無效位置寫入終止零字節）。

您可以使用%c轉換說明符讀取單個字符。