Understanding of write file operation in char driver

[me storage]

I am learning char drivers.But i didn't understand write operation of char
device driver properly. the below is my write operation

static ssize_t dev_write(struct file *fil,const char __user
*buff,size_t len,loff_t *off)
{
    pr_info("user input string %s\n",buff);
    pr_info("user input string len %d\n",len);
    return len;
}

my doubt is if i write into my device like
echo "hello" > /dev/myDev

it is giving different behaviour like below is the dmesg
[20596.975355] user input string hello
[20596.975355] 77b9e4
[20596.975355] insmod insmod
[20596.975355] n/zeitgeist-daemon
[20596.975355] atives
[20596.975355]
[20596.975355] vars "${upargs[@]}"
[20596.975355]  cur cword words=();
[20596.975355]     local upargs=() upvars=() vcur vcword vprev vwords;
[20596.975355]     while getopts "c:i:n:p:w:" flag "$@"; do
[20596.975355]         case $flag in
[20596.975355]             c)
[20596.975355]                 vcur=$OPTARG
[20596.975355]             ;;
[20596.975355]             i)
[20596.975355]                 vcword=$OPTARG
[20596.975355]             ;;
[20596.975355]             n)
[20596.975355]                 exclude=$OPTARG
[20596.975355]             ;;
[20596.975355]             p)
[20596.975355]                 vprev=$OPTARG
[20596.975355]             ;;
[20596.975355]             w)
[20596.975355]                 vwords=$OPTARG
[20596.975355]             ;;
[20596.975358] user input string len 6
[20596.975361] Device closed

so i didn't understand what is happening inside .Can any one please
explain what is happening?

Thanks & Regards
Prasad
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