command sleep

sleep.c

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

static void Usage(const char *name)
{
    printf("%s NUMBER[SUFFIX]...\n\n", name);
    printf("The sleep command pauses for an amount of time defined by NUMBER. NUMBER must be an integer. floating-point value is NOT support.\n");
    printf("SUFFIX may be \"s\" for seconds (the default), \"m\" for minutes, \"h\" for hours, or \"d\" for days.\n");
    printf("If more than one NUMBER is specified, sleep delays for the sum of their values.\n");
}

static unsigned long int calctime(const char *ptime)
{
    int i = 0;
    unsigned long int timelen = 0;
    unsigned long int len = strlen(ptime);
    char suffix = 's';

    if(len > 1)
    {
        suffix = ptime[len - 1];
    }

    timelen = strtoul(ptime, NULL, 10);

    switch(suffix)
    {
        case 's':
            break;

        case 'm':
            timelen = timelen * 60;
            break;

        case 'h':
            timelen = timelen  * 60 * 60;
            break;

        case 'd':
            timelen = timelen * 24 * 60 * 60;
            break;

        default:
            break;
    }

    return timelen;
}

int main(int argc, char *argv[])
{
    unsigned long int timelen = 0;
    int i = 0;

    if(1 == argc)
    {
        Usage(argv[0]);
        return -1;
    }

    for(i = 1; i < argc; i++)
    {
        timelen += calctime(argv[i]);
    }

    if(timelen > 0)
    {
        sleep(timelen);
    }

    return 0;
}