[英]C code to count the number of characters, words and lines in a file
我是C的初學者,所以我想看一段代碼,該代碼包含對給定文件中的字符,單詞和行數進行計數。 我在下面的代碼中找到了問題,但我不明白為什么我們必須在while循環后增加最后一個單詞的單詞和行數: 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;
}
該程序有一些問題:
ch
必須定義為int
,以便正確檢測EOF
。
scanf("%s", path);
超長輸入scanf("%s", path);
將溢出path
並導致未定義的行為。 還要檢查返回值以檢測無效的輸入或文件的提前結束:
if (scanf("%99s", path) != 1) return 1;
測試ch == '\\0'
以計算行數是有爭議的。 標准的wc
unix實用程序不會將空字節用作行分隔符。
if (ch == ' ' || ch == '\\t' || ch == '\\n' || ch == '\\0')
也不是檢測單詞邊界的標准方法。 if (isspace(ch))
更慣用。
字數錯誤:多個空格將計為多個字! 您應該改為檢測邊界,即空格字符后跟非空格字符。
最后的測試是解決上述問題的la腳嘗試,但這還不夠。 如果流不以換行符結尾,則確實需要進行額外的測試以計算流的最后一位。
這是更正的版本:
#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;
}
根據輸入的輸入文件是否以漂亮的換行符('\\ n')結尾,將需要調整輸出。
對於在所有行(包括最后一行)都以'\\ n'結尾的普通sain文本文件,請在循環后刪除這些增量。
但是對於這些特殊情況,似乎需要對程序進行一些調試,這取決於您的定義。 但是我強烈建議使用Linux / Unix命令wc
作為參考和決勝局。
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