Conditional jump or move depends on uninitialized value(s) on strlen(s)-CodePudding

My C code below is trying to remove the trailing white space from a string pointer. while testing the code I am getting a "Conditional jump or move depends on the uninitialized value(s)" a line 3. Since I am trying to read the length of a string pointer, do I need to initialize it?

void trim(char *s)
{
    int i = strlen(s) - 1;
 
    while (i > 0)
    {
        if (s[i] == ' ' || s[i] == '\t')
            i--;
        else /* where you see very first from the last nonwhite space*/
            break;
    }
    s[i   1] = '\0';

}

function trim is called in another function which is reading input from commandline

char *UserInput()
{
    char *input = (char *)malloc(120);

    char command[120];
    int len = read(STDIN_FILENO, command, 120 - 1);
    int i;
    for (i = 0; i < len; i  )
    {
        if (command[i] == '\n')
        {
            break;
        }
        input[i] = command[i];
    }
    trim(input);
    return input;
}

CodePudding user response：

Your copying of command to input character by character fails to terminate it with a NUL character, giving undefined behavior when you call strlen on the parameter passed to trim

Fix:

input[i] = '\0';
trim(input);