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