文件中的回車符

有人可以爲我解開這個謎嗎？
我讀到 '/ r' 和 '/ N' 之間的區別，這不是我要問...文件中的回車符

考慮這兩個文件：
的config.txt：

home/my_user/Documents/prog/my_folder 
home/my_user/Documents/prog/IO/input_for_prog.txt 
home/my_user/Documents/prog/IO/correct_output.txt

的test.txt：

This is a test file 
Why isn't there carriage return char 
at the end of each line in this file?

現在，考慮下面的代碼：

int main(int argc, char* argv[]) { 

    int fd=open(argv[1], O_RDONLY); 
    if (fd==-1) { 
     perror("Error opening"); 
     return -1; 
    } 

    char ch; 
    int ret_code; 

    while ((ret_code=read(fd, &ch, 1))!=0) { 

     if (ret_code==-1) { 
      perror("Error reading"); 
      return -1; 
     } 

     printf("Character is: %c, its ascii value: %d\n", ch, ch); 
    } 
}

只是暫時忽略潛在的錯誤，因爲這不是問題在這裏（我希望）。此代碼將只打印文件中的每個字符，並且它是ascii值。

現在，看的時候我在上述文件中運行它時會發生什麼？
輸出爲的config.txt：

Character is: h, its ascii value: 104 
Character is: o, its ascii value: 111 
Character is: m, its ascii value: 109 
Character is: e, its ascii value: 101 
Character is: /, its ascii value: 47 
Character is: m, its ascii value: 109 
Character is: y, its ascii value: 121 
Character is: _, its ascii value: 95 
Character is: u, its ascii value: 117 
Character is: s, its ascii value: 115 
Character is: e, its ascii value: 101 
Character is: r, its ascii value: 114 
Character is: /, its ascii value: 47 
Character is: D, its ascii value: 68 
Character is: o, its ascii value: 111 
Character is: c, its ascii value: 99 
Character is: u, its ascii value: 117 
Character is: m, its ascii value: 109 
Character is: e, its ascii value: 101 
Character is: n, its ascii value: 110 
Character is: t, its ascii value: 116 
Character is: s, its ascii value: 115 
Character is: /, its ascii value: 47 
Character is: p, its ascii value: 112 
Character is: r, its ascii value: 114 
Character is: o, its ascii value: 111 
Character is: g, its ascii value: 103 
Character is: /, its ascii value: 47 
Character is: m, its ascii value: 109 
Character is: y, its ascii value: 121 
Character is: _, its ascii value: 95 
Character is: f, its ascii value: 102 
Character is: o, its ascii value: 111 
Character is: l, its ascii value: 108 
Character is: d, its ascii value: 100 
Character is: e, its ascii value: 101 
Character is: r, its ascii value: 114 
, its ascii value: 13 
Character is: 
, its ascii value: 10 
Character is: h, its ascii value: 104 
Character is: o, its ascii value: 111 
Character is: m, its ascii value: 109 
Character is: e, its ascii value: 101 
Character is: /, its ascii value: 47 
Character is: m, its ascii value: 109 
Character is: y, its ascii value: 121 
Character is: _, its ascii value: 95 
Character is: u, its ascii value: 117 
Character is: s, its ascii value: 115 
Character is: e, its ascii value: 101 
Character is: r, its ascii value: 114 
Character is: /, its ascii value: 47 
Character is: D, its ascii value: 68 
Character is: o, its ascii value: 111 
Character is: c, its ascii value: 99 
Character is: u, its ascii value: 117 
Character is: m, its ascii value: 109 
Character is: e, its ascii value: 101 
Character is: n, its ascii value: 110 
Character is: t, its ascii value: 116 
Character is: s, its ascii value: 115 
Character is: /, its ascii value: 47 
Character is: p, its ascii value: 112 
Character is: r, its ascii value: 114 
Character is: o, its ascii value: 111 
Character is: g, its ascii value: 103 
Character is: /, its ascii value: 47 
Character is: I, its ascii value: 73 
Character is: O, its ascii value: 79 
Character is: /, its ascii value: 47 
Character is: i, its ascii value: 105 
Character is: n, its ascii value: 110 
Character is: p, its ascii value: 112 
Character is: u, its ascii value: 117 
Character is: t, its ascii value: 116 
Character is: _, its ascii value: 95 
Character is: f, its ascii value: 102 
Character is: o, its ascii value: 111 
Character is: r, its ascii value: 114 
Character is: _, its ascii value: 95 
Character is: p, its ascii value: 112 
Character is: r, its ascii value: 114 
Character is: o, its ascii value: 111 
Character is: g, its ascii value: 103 
Character is: ., its ascii value: 46 
Character is: t, its ascii value: 116 
Character is: x, its ascii value: 120 
Character is: t, its ascii value: 116 
, its ascii value: 13 
Character is: 
, its ascii value: 10 
Character is: h, its ascii value: 104 
Character is: o, its ascii value: 111 
Character is: m, its ascii value: 109 
Character is: e, its ascii value: 101 
Character is: /, its ascii value: 47 
Character is: m, its ascii value: 109 
Character is: y, its ascii value: 121 
Character is: _, its ascii value: 95 
Character is: u, its ascii value: 117 
Character is: s, its ascii value: 115 
Character is: e, its ascii value: 101 
Character is: r, its ascii value: 114 
Character is: /, its ascii value: 47 
Character is: D, its ascii value: 68 
Character is: o, its ascii value: 111 
Character is: c, its ascii value: 99 
Character is: u, its ascii value: 117 
Character is: m, its ascii value: 109 
Character is: e, its ascii value: 101 
Character is: n, its ascii value: 110 
Character is: t, its ascii value: 116 
Character is: s, its ascii value: 115 
Character is: /, its ascii value: 47 
Character is: p, its ascii value: 112 
Character is: r, its ascii value: 114 
Character is: o, its ascii value: 111 
Character is: g, its ascii value: 103 
Character is: /, its ascii value: 47 
Character is: I, its ascii value: 73 
Character is: O, its ascii value: 79 
Character is: /, its ascii value: 47 
Character is: c, its ascii value: 99 
Character is: o, its ascii value: 111 
Character is: r, its ascii value: 114 
Character is: r, its ascii value: 114 
Character is: e, its ascii value: 101 
Character is: c, its ascii value: 99 
Character is: t, its ascii value: 116 
Character is: _, its ascii value: 95 
Character is: o, its ascii value: 111 
Character is: u, its ascii value: 117 
Character is: t, its ascii value: 116 
Character is: p, its ascii value: 112 
Character is: u, its ascii value: 117 
Character is: t, its ascii value: 116 
Character is: ., its ascii value: 46 
Character is: t, its ascii value: 116 
Character is: x, its ascii value: 120 
Character is: t, its ascii value: 116 
, its ascii value: 13 
Character is: 
, its ascii value: 10

輸出爲的test.txt：

Character is: T, its ascii value: 84 
Character is: h, its ascii value: 104 
Character is: i, its ascii value: 105 
Character is: s, its ascii value: 115 
Character is: , its ascii value: 32 
Character is: i, its ascii value: 105 
Character is: s, its ascii value: 115 
Character is: , its ascii value: 32 
Character is: a, its ascii value: 97 
Character is: , its ascii value: 32 
Character is: t, its ascii value: 116 
Character is: e, its ascii value: 101 
Character is: s, its ascii value: 115 
Character is: t, its ascii value: 116 
Character is: , its ascii value: 32 
Character is: f, its ascii value: 102 
Character is: i, its ascii value: 105 
Character is: l, its ascii value: 108 
Character is: e, its ascii value: 101 
Character is: 
, its ascii value: 10 
Character is: W, its ascii value: 87 
Character is: h, its ascii value: 104 
Character is: y, its ascii value: 121 
Character is: , its ascii value: 32 
Character is: i, its ascii value: 105 
Character is: s, its ascii value: 115 
Character is: n, its ascii value: 110 
Character is: ', its ascii value: 39 
Character is: t, its ascii value: 116 
Character is: , its ascii value: 32 
Character is: t, its ascii value: 116 
Character is: h, its ascii value: 104 
Character is: e, its ascii value: 101 
Character is: r, its ascii value: 114 
Character is: e, its ascii value: 101 
Character is: , its ascii value: 32 
Character is: c, its ascii value: 99 
Character is: a, its ascii value: 97 
Character is: r, its ascii value: 114 
Character is: r, its ascii value: 114 
Character is: i, its ascii value: 105 
Character is: a, its ascii value: 97 
Character is: g, its ascii value: 103 
Character is: e, its ascii value: 101 
Character is: , its ascii value: 32 
Character is: r, its ascii value: 114 
Character is: e, its ascii value: 101 
Character is: t, its ascii value: 116 
Character is: u, its ascii value: 117 
Character is: r, its ascii value: 114 
Character is: n, its ascii value: 110 
Character is: , its ascii value: 32 
Character is: c, its ascii value: 99 
Character is: h, its ascii value: 104 
Character is: a, its ascii value: 97 
Character is: r, its ascii value: 114 
Character is: 
, its ascii value: 10 
Character is: a, its ascii value: 97 
Character is: t, its ascii value: 116 
Character is: , its ascii value: 32 
Character is: t, its ascii value: 116 
Character is: h, its ascii value: 104 
Character is: e, its ascii value: 101 
Character is: , its ascii value: 32 
Character is: e, its ascii value: 101 
Character is: n, its ascii value: 110 
Character is: d, its ascii value: 100 
Character is: , its ascii value: 32 
Character is: o, its ascii value: 111 
Character is: f, its ascii value: 102 
Character is: , its ascii value: 32 
Character is: e, its ascii value: 101 
Character is: a, its ascii value: 97 
Character is: c, its ascii value: 99 
Character is: h, its ascii value: 104 
Character is: , its ascii value: 32 
Character is: l, its ascii value: 108 
Character is: i, its ascii value: 105 
Character is: n, its ascii value: 110 
Character is: e, its ascii value: 101 
Character is: , its ascii value: 32 
Character is: i, its ascii value: 105 
Character is: n, its ascii value: 110 
Character is: , its ascii value: 32 
Character is: t, its ascii value: 116 
Character is: h, its ascii value: 104 
Character is: i, its ascii value: 105 
Character is: s, its ascii value: 115 
Character is: , its ascii value: 32 
Character is: f, its ascii value: 102 
Character is: i, its ascii value: 105 
Character is: l, its ascii value: 108 
Character is: e, its ascii value: 101 
Character is: ?, its ascii value: 63 
Character is: 
, its ascii value: 10

我注意到了幾件事，並且找不到答案：
首先，如test.txt文件建議，爲什麼在這個文件的每行末尾沒有'/ r'char ，而在config.txt中有'/ r'和'/ n'在每行的結尾？
二，爲什麼「字符是」字樣消失在它印刷的線條上「，其ASCII值爲13」 ??

謝謝。

來源

2014-04-02 so.very.tired

當打印到控制檯窗口（即不是文件）時，\r指示它返回到行的開頭（因此您的「Character is」文本消失）。然而，\n指示它走下一條線。例如，\r對於顯示同一行上的進度很有用。

文件可以被保存或者\r\n，\n或\r在每行的末尾（見下文評論），這幾天被解釋的文本編輯器一樣（其實很多警告你，如果你混的文件中的類型）。看起來你有一個文件\r\n，另一個文件只有\n。

來源

2014-04-02 12:29:40 noelicus

某些系統在一行的末尾還使用'\ r'保存文件，所以選項是'\ n'（對於類似nix的系統），'\ r \ n'（主要是窗口）和'\ r'（老蘋果機器人，在某些情況下OS X，我似乎記得） –

酷 - 更新的答案包括'\ r'。謝謝！ – noelicus

如果OP不想編寫代碼來「壓扁」任何可能的CR/LF，我建議使用'fopen'以文本模式（'「rt」'）和'fgets'打開文件。 – usr2564301

我無法回答這兩個文件之間的差異，因爲我沒有它們，也沒有辦法創建它們。

這就是說，ASCII值13和ASCII值10是不可打印的字符。意思是，除非你檢測並翻譯了看起來是用於控制回車和/或換行到\r或\n的看不見的字符的值，那麼你就不會「看見」它。

來源

2014-04-02 12:27:59 Brian

「Character is」消失的原因是\ 13字符是回車符。它將光標放回到行的開頭，這樣文本的其餘部分「，其ascii值是...」將覆蓋它。

只有\ n（新行）或\ r \ n（回車和新行）纔有效。

來源

2014-04-02 12:29:50 Trenin

行尾差異可能由各種原因引起，例如，使用不同的文本編輯器。

至於\n和\r人物，他們執行以下操作：

\n插入符移動到下一行
\r將插入符移動到當前行的開頭

有了這些知識，你應該能夠理解程序的輸出。這是「正常」的角色：

Character is: t, its ascii value: 116

這是\r，注意插入符號是如何被移動到行的開頭時，它已經被印：

, its ascii value: 13

這是\n，注意如何插入符號已經移動到下一行的時候已經打印了：

Character is: 
, its ascii value: 10

來源

2014-04-02 12:33:11 Andrey

謝謝大家的好評！這解釋了很多。 –

的第一個問題是我們無法解決的，因爲我們不知道如何將文件被創建。 Windows程序通常使用'\ r \ n'，而Linux'\ n'就足夠了。

第二個問題很容易回答，你打印「字符是：\ n，它...」，所以你會得到一個換行符。除非你轉義特殊字符，否則你不能打印換行符。

編輯您可能想要越過\ r & \ n，就像標籤和其他人一樣。請參閱here

來源

2014-04-02 12:33:57 Mathias

「我們無法解決第一個問題，因爲我們不知道文件是如何創建的，Windows程序通常使用'\ r \ n'，而對於Linux'\ n'就足夠了。」很棒，這正是我在第一個問題中尋找的答案，這取決於文件的創建方式和位置，這是我需要的信息...... –

文件中的回車符

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