文件中的回车符

Question

文件中的回车符

有人可以帮我解决这个谜......
我读到'/ r'和'/ n'之间的区别,这不是我想问的问题......

考虑这两个文件:
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

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的test.txt:

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

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现在,请考虑以下代码:

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);
    }
}

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暂时忽略潜在的错误,因为这不是问题(我希望).这段代码只打印文件中的每个字符,它的ascii值.

现在,看看当我在上面的文件上运行它时会发生什么...
输出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

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test.txt的输出:

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

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我注意到的一些事情,但无法找到答案:
首先,正如test.txt文件所示,为什么在这个文件的每行末尾都没有'/ r'字符,而在config中. txt在每一行的末尾都有'/ r' 和 '/ n'？
第二,为什么"Character is"这个词在它打印的行上消失了",它的ascii值是13"？

谢谢.

Answer 1

noe*_*cus 5

当打印到控制台窗口(即不是文件)时,\r指示它返回到行的开头(因此"Character is"文本消失).的\n,然而,指示它去下一行.的\r是表示在同一行上的进步,例如有用的.

文件可以保存要么\r\n,\n或\r在每行的末尾(见下文评论),这几天被解释的文本编辑器一样(其实很多警告你,如果你在一个文件中混合类型).看起来你有一个文件,\r\n另一个只有\n.

@Jongware注意:使用`fopen()`,`"r"`打开一个文本文件进行阅读.使用"rt"`在许多系统上也是如此,但按规范,行为是未定义的. (2认同)
+1为最佳答案."\n,然而,指示它去下一行"是真的,但请注意更多细节,在某些控制台上,这将保持水平偏移(因此通常存在伴侣''\ r'`).在其他游戏机上,即使没有伴奏"\n","'\n"也会执行"回到行的开头". (2认同)

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