如題,程式碼如下:

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

//空白字元有: ' '(中間是空格), \t, \r, \n
char* trim(char *str) {
	int first = -1; //第一個空白字元的下標
	int last = -1; //最後一個空白字元的下標
	//找到第一個非空白字元
	for (int i = 0; str[i] != '\0'; i++) {
		if (str[i] != ' '
			&& str[i] != '\t'
			&& str[i] != '\n'
			&& str[i] != '\r') {
			first = i;
			break;
		}
	}
	if (first == -1) { //全是空白字元
		str[0] = '\0';
		return str;
	}

	//儲存最後一個非空白字元的指標
	for (int i = first; str[i] != '\0'; i++) {
		if (str[i] != ' '
			&& str[i] != '\t'
			&& str[i] != '\n'
			&& str[i] != '\r') {
			last = i;
		}
	}

	//在最後一個非空白字元的後面賦值'\0'
	str[last + 1] = '\0';
	return str + first;
}
int main() {
	//測試資料
	char strs[][40] = {
		"",
		"      ",
		"   akklp  ",
		"  fsj dfk ",
		"     aaaa\t   \r\nbbbb  \t    \r  \n   "
	}; //注意\r是回到當前行的開頭,利用\r能夠覆寫已經列印的字元
	for (int i = 0; i < 5; i++) {
		char *res = trim(strs[i]);
		printf("#%s#\n", res);
	}
	return 0;
}
 

實現效果如圖: