去掉字符串前后的空格

#include <stdio.h>
#include <string.h>
#include <ctype.h>
char *strtrimr(char *pstr)
{
	int i;
	i = strlen(pstr) - 1;
	while (isspace(pstr[i]) && (i >= 0))
		pstr[i--] = '\0';
	return pstr;
}

char *strtriml(char *pstr)
{
	int i = 0,j;
	j = strlen(pstr) - 1;
	while (isspace(pstr[i]) && (i <= j))
		i++;
	if (0<i)
		strcpy(pstr, &pstr[i]);
	return pstr;
}

char *strtrim(char *pstr)
{
	char *p;
	p = strtrimr(pstr);
	return strtriml(p);
}

int main(void)
{
	char str1[] = "   ackerman zhang";
	char str2[] = "ackerman zhang   ";
	char str3[] = "   ackerman zhang   ";
	
	printf("\nBefore convertion:\n\t\"%s\"\n\t\"%s\"\n\t\"%s\"\n",
               str1, str2, str3);

	char *p1,*p2,*p3;
	p1=strtriml(str1);
	p2=strtrimr(str2);
	p3=strtrim(str3);

	printf("\nAfter convertion:\n\t\"%s\"\n\t\"%s\"\n\t\"%s\"\n",
	       p1,p2,p3);

	return 0;
}