Linux 使用 C 计算行数
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Count number of line using C
提问by tariq
Is there a way to count the number of lines in my file using C?
有没有办法使用 C 计算我的文件中的行数？
采纳答案by Shamim Hafiz
If you want to perform this programmatically, open the file in text mode and perform fgetc() operation until you reach end of file. Keep a count of number of times fgetc was called.
如果要以编程方式执行此操作，请以文本模式打开文件并执行 fgetc() 操作，直到到达文件末尾。记录调用 fgetc 的次数。
FILE *fp = fopen("myfile.txt");
int ch;
int count=0;
do
{
ch = fgetc(fp);
if(ch == '\n') count++;
} while( ch != EOF );
printf("Total number of lines %d\n",count);
回答by Ben Voigt
Try the wccommand. Most linux distributions include it.
试试这个wc命令。大多数 linux 发行版都包含它。
回答by COrthbandt
If you are referring to the line number withinyour c source, most compilers support the __LINE__macro.
If you want to count line numbers of arbitrary text files inc, the following functions should be starting points:
如果你指的是行号内的C源，大多数编译器支持__LINE__宏。如果你要计算的任意文本文件的行号在C，以下功能应该开始点：
- fopen() to open a file for reading
- fgets() to read lines
- eof() to check for end of file
- fclose() to close the file
- fopen() 打开一个文件进行读取
- fgets() 读取行
- eof() 检查文件结尾
- fclose() 关闭文件
Combining these into a line counter is left as an exercise to the reader :)
将这些组合成一个行计数器留给读者作为练习:)
回答by Pete Wilson
Please think for a moment about what you have to do to count lines in a file:
请想一想你需要做什么来计算文件中的行数：
Open the file for reading, maybe with fopen( );
Read each line, one line at a time, maybe with fread( );
Increment a line counter that you've initialized to zero earlier;
Whwn end-of-file is returned from the next read of the file, you are done. printf( ) the line counter.
打开文件进行读取，可能使用 fopen( );
读取每一行，一次一行，可能使用 fread()；
增加一个你之前初始化为零的行计数器；
当文件的下一次读取返回文件结束时，您就完成了。printf() 行计数器。
回答by David C. Rankin
One nagging issue that can effect the number of lines returned regardless of the method you use is whether the file contains a POSIX compliant '\n'at the end of the last line. There are a number of editors (and programs) that happily write the final amount of text to a file without the POSIX end-of-line. You can handle either case regardless of which method you use to determine the number of lines in a file.
无论您使用何种方法，都会影响返回的行数的一个令人烦恼的问题是文件是否'\n'在最后一行的末尾包含符合 POSIX 的文件。有许多编辑器（和程序）可以愉快地将最终文本量写入文件，而无需 POSIX 行尾。无论您使用哪种方法来确定文件中的行数，您都可以处理任何一种情况。
If you are trying to determine the number of line in a largefile, then you will definitely want a buffered read (e.g. reading multiple characters into a buffer, per-read) rather than a character-by-characterapproach. The can greatly improve the efficiency.
如果您试图确定大文件中的行数，那么您肯定需要缓冲读取（例如，将多个字符读入缓冲区，每次读取）而不是逐个字符的方法。可以大大提高效率。
Putting those two pieces together, you can use either fgetsor POSIX getlineto determine the number of lines in a file fairly efficiently. For example with getline(which handles the line-end issue or you), you could do:
将这两部分放在一起，您可以使用fgetsPOSIX 或 POSIXgetline来相当有效地确定文件中的行数。例如使用getline（处理行尾问题或您），您可以执行以下操作：
/** open and read each line in 'fn' returning the number of lines */
size_t nlinesgl (char *fn)
{
if (!fn) return 0;
size_t lines = 0, n = 0;
char *buf = NULL;
FILE *fp = fopen (fn, "r");
if (!fp) return 0;
while (getline (&buf, &n, fp) != -1) lines++;
fclose (fp);
free (buf);
return lines;
}
With fgets, testing for additional text after the final newlineis up to you, e.g.
使用fgets，在最终换行符之后测试其他文本取决于您，例如
/** note; when reading with fgets, you must allow multiple reads until
* '\n' is encountered, but you must protect against a non-POSIX line
* end with no '\n' or your count will be short by 1-line. the 'noeol'
* flag accounts for text without a '\n' as the last line in the file.
*/
size_t nlines (char *fn)
{
if (!fn) return 0;
size_t n = 0, noeol = 0;
char buf[FILENAME_MAX] = "";
FILE *fp = fopen (fn, "r");
if (!fp) return 0;
while (fgets (buf, FILENAME_MAX, fp)) {
noeol = 0;
if (!strchr (buf, '\n')) {
noeol = 1; /* noeol flag for last line */
continue;
}
n++;
}
if (noeol) n++; /* check if noeol, add 1 */
fclose (fp);
return n;
}
(note:you can add your own code to handle a fopenfailure in each function.)
（注意：您可以添加自己的代码来处理fopen每个函数中的失败。）
