remove white spaces (frontside and backside)

test-strtrim.c

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

static void strtrim(char *inout)
{
    char *start = inout;
    char *end = inout + strlen(inout) - 1;
    int i;

    while (isspace(*start)) { start++; }
    while (isspace(*end) && (end-start) > 0) { *end = '\0'; end--; }

    if (start != inout) {
        strcpy(inout, start);
    }
}

int main()
{
    char str[][10] = {
        " hello",
        "hello ",
        "  hello",
        "hello  ",
        " ",
        "",
    };

    for (int i = 0; i < 6; i++) {
        printf("[%s] > ", str[i]);
        strtrim(str[i]);
        printf(" > [%s]\n", str[i]);
    }
    return 0;
}

/*
output
-----------------------------------
[ hello] >  > [hello]
[hello ] >  > [hello]
[  hello] >  > [hello]
[hello  ] >  > [hello]
[ ] >  > []
[] >  > []
-----------------------------------
*/