我是 C 的初学者,所以我想看看一个代码,它包括计算给定文件中的字符数、单词数和行数。我发现了下面的代码,但问题是我不明白为什么我们必须在 while 循环之后增加最后一个单词的单词和行:if (characters > 0)...
#include <stdio.h>
#include <stdlib.h>
int main() {
FILE *file;
char path[100];
char ch;
int characters, words, lines;
/* Input path of files to merge to third file */
printf("Enter source file path: ");
scanf("%s", path);
/* Open source files in 'r' mode */
file = fopen(path, "r");
/* Check if file opened successfully */
if (file == NULL) {
printf("\nUnable to open file.\n");
printf("Please check if file exists and you have read privilege.\n");
exit(EXIT_FAILURE);
}
/*
* Logic to count characters, words and lines.
*/
characters = words = lines = 0;
while ((ch = fgetc(file)) != EOF) {
characters++;
/* Check new line */
if (ch == '\n' || ch == '\0')
lines++;
/* Check words */
if (ch == ' ' || ch == '\t' || ch == '\n' || ch == '\0')
words++;
}
/* Increment words and lines for last word */
if (characters > 0) {
words++;
lines++;
}
/* Print file statistics */
printf("\n");
printf("Total characters = %d\n", characters);
printf("Total words = %d\n", words);
printf("Total lines = %d\n", lines);
/* Close files to release resources */
fclose(file);
return 0;
}
最佳答案
这个程序有一些问题:
ch
必须定义为int
以允许正确检测EOF
。scanf("%s", path);
的输入过长将导致path
溢出并导致未定义的行为。还要检查返回值以检测无效输入或文件过早结束:if (scanf("%99s", path) != 1) return 1;
测试
ch == '\0'
来计算行数是有争议的。标准wc
unix 实用程序不会将空字节视为行分隔符。if (ch == ' ' || ch == '\t' || ch == '\n' || ch == '\0')
也是不是检测单词边界的标准方法。if (isspace(ch))
更加地道。字数不正确:多个空格将被视为多个字!您应该改为检测边界,即空格字符后跟非空格字符。
最后的测试是解决上述问题的蹩脚尝试,它还不够。如果流不以换行符结束,则确实需要额外的测试来计算流的最后一个。
这是一个更正的版本:
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
int main() {
FILE *file;
char path[1024];
int ch, last;
long long int characters, words, lines;
/* Input path of files to merge to third file */
printf("Enter source file path: ");
if (scanf("%255s", path) != 1) {
printf("Invalid input\n");
return EXIT_FAILURE;
}
/* Open source files in 'r' mode */
file = fopen(path, "r");
/* Check if file opened successfully */
if (file == NULL) {
printf("Unable to open file %s\n", path);
printf("Please check if file exists and you have read privilege.\n");
return EXIT_FAILURE;
}
/*
* Logic to count characters, words and lines.
*/
characters = words = lines = 0;
last = '\n';
while ((ch = fgetc(file)) != EOF) {
characters++;
/* Check new line */
if (ch == '\n')
lines++;
/* Check words */
if (!isspace(ch) && isspace(last))
words++;
last = ch;
}
/* Increment words and lines for last word */
if (last != '\n') {
lines++;
}
/* Print file statistics */
printf("\n");
printf("Total characters = %lld\n", characters);
printf("Total words = %lld\n", words);
printf("Total lines = %lld\n", lines);
/* Close file to release resources */
fclose(file);
return 0;
}
关于计算文件中字符数、单词数和行数的C代码,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54845010/