Linux World: 2018

Create animated 2019 on terminal

The above animation can be generated on the termnal using the following script.

#!/bin/bash

#create 2017 on terminal using any user specified character
str_dwn() {
rows=$1
s_start=$2
char=$4
str_st_row=$3
rows_end=$((str_st_row+rows))
for((i=str_st_row;i<rows_end;i++))
do 
tput cup $i $s_start
printf "$char " 
done
echo""
}

backslash() {
b_st_row=$1
b_st_cols=$2
b_char=$3
b_r_end=$((b_st_row + 5 ))
for((p=b_st_row;p<b_r_end;p++))
do 
tput setaf $4
tput cup $p $b_st_cols
printf "$b_char " 
((b_st_cols++))
done
echo""
}

forward() {
f_st_row=$1
f_st_cols=$2
f_len=$3
f_char=$4

f_r_end=$((f_st_row + $f_len))

for((i=f_st_row;i<f_r_end;i++))
do 
tput cup $i $f_st_cols
printf "$f_char "
 ((f_st_cols--))
done
echo""

}

horizontal() {
hrow=$2
hstart=$1
hcols=$3
char=$4

end=$((hstart + hcols))

for((i=hstart;i<=end;i++))
do 
tput cup $hrow $i
printf "$char" 
done
echo""
}

half_horizontal() {
hrow=$2
hstart=$1
hcols=$(($3/2))
char=$4

end=$((hstart + hcols))

for((i=hstart;i<=end;i++))
do 
tput cup $hrow $i
printf "$char" 
done
echo""
}

gen_rand() {
num1=$1

if [ $num1 -eq 0 ]
then
temp=$(($RANDOM % 2))
rand=$((temp + 2))

else

temp=$(($RANDOM % 5))
rand=$((temp + num1))
fi
}

two() {

hstart_2=$1
hrow_be=$2
hcols_2=$3
char=$4
color=$5

set_color

horizontal $hstart_2 $hrow_be $hcols_2 "$char"

st_row_2=$((hrow_be+1))
f_st_cols_2=$((hstart_2+hcols_2))

forward $st_row_2 $f_st_cols_2 5 "$char" $color
hstart_2_lo=$start
hrow_2_lo=$((hrow_be+6))
hcols_2_lo=5
horizontal $hstart_2_lo $hrow_2_lo $hcols_2_lo "$char"

}

zero() {

set_color

hstart_0=$((f_st_cols_2 +4))
hcols_0=5
horizontal $hstart_0 $hrow_be $hcols_0 "$char"

str_dwn_col_0=$hstart_0
str_dwn_row_0=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_0 $str_dwn_row_0 "$char"

hstart_0_lo=$((f_st_cols_2 +4))
hcols_0_lo=6
hrow_0_lo=$((hrow_be+6))
horizontal $hstart_0 $hrow_0_lo $hcols_0 "$char"

str_dwn_col_rig_0=$((hstart_0 +5))
str_dwn_row_rig_0=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_rig_0 $str_dwn_row_rig_0 "$char"
}

one() {
set_color
str_dwn_col_1=$((str_dwn_col_rig_0 + 4))
str_dwn_row_1=$((hrow_be))
str_dwn 7 $str_dwn_col_1 $str_dwn_row_1 "$char"

}

nine() {
set_color

set_color

hstart_8=$((str_dwn_col_1 +4))
hcols_8=5
horizontal $hstart_8 $hrow_be $hcols_8 "$char"

str_dwn_col_8=$hstart_8
str_dwn_row_8=$((hrow_be + 1))
str_dwn 3 $str_dwn_col_8 $str_dwn_row_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+6))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

str_dwn_col_rig_8=$((hstart_8 +5))
str_dwn_row_rig_8=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_rig_8 $str_dwn_row_rig_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+3))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

}

five() {
set_color

set_color

#hstart_8=$((str_dwn_col_1 +4))
#hcols_8=5
#horizontal $hstart_8 $hrow_be $hcols_8 "$char"

str_dwn_col_8=$hstart_8
str_dwn_row_8=$((hrow_be + 1))
str_dwn 3 $str_dwn_col_8 $str_dwn_row_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+6))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

str_dwn_col_rig_8=$((hstart_8 +5))
str_dwn_row_rig_8=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_rig_8 $str_dwn_row_rig_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+3))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

}

set_color(){
color=$RANDOM 
color=$((color%6))
tput setaf $color
}

cols=`tput cols`
mid=$((cols/2))
start=$((mid-16))
#echo "What character do you want to use"
#read char
char="*"

tput clear
rows=5

begin_row=2
num_cols=6

two $start $begin_row $num_cols "$char" $color;zero;one;nine

tput setaf 7
tput cup 9 0

Save the script as 2019.sh and run on the terminal to generate the animation.

Create a countdown to 2019

Save the following script as countdown2019.sh

str_dwn() {
rows=$1
s_start=$2
char=$4
str_st_row=$3
rows_end=$((str_st_row+rows))
for((i=str_st_row;i<rows_end;i++))
do 
tput cup $i $s_start
printf "$char " 
done
echo""
}

backslash() {
b_st_row=$1
b_st_cols=$2
b_char=$3
b_r_end=$((b_st_row + 5 ))
for((p=b_st_row;p<b_r_end;p++))
do 
tput setaf $4
tput cup $p $b_st_cols
printf "$b_char " 
((b_st_cols++))
done
echo""
}

forward() {
f_st_row=$1
f_st_cols=$2
f_len=$3
f_char=$4

f_r_end=$((f_st_row + $f_len))

for((i=f_st_row;i<f_r_end;i++))
do 
tput cup $i $f_st_cols
printf "$f_char "
 ((f_st_cols--))
done
echo""

}

horizontal() {
hrow=$2
hstart=$1
hcols=$3
char=$4

end=$((hstart + hcols))

for((i=hstart;i<=end;i++))
do 
tput cup $hrow $i
printf "$char" 
done
echo""
}

half_horizontal() {
hrow=$2
hstart=$1
hcols=$(($3/2))
char=$4

end=$((hstart + hcols))

for((i=hstart;i<=end;i++))
do 
tput cup $hrow $i
printf "$char" 
done
echo""
}

gen_rand() {
num1=$1

if [ $num1 -eq 0 ]
then
temp=$(($RANDOM % 2))
rand=$((temp + 2))

else

temp=$(($RANDOM % 5))
rand=$((temp + num1))
fi
}

two() {

hstart_2=$1
hrow_be=$2
hcols_2=$3
char=$4
color=$5

set_color

horizontal $hstart_2 $hrow_be $hcols_2 "$char"

st_row_2=$((hrow_be+1))
f_st_cols_2=$((hstart_2+hcols_2))

forward $st_row_2 $f_st_cols_2 5 "$char" $color
hstart_2_lo=$start
hrow_2_lo=$((hrow_be+6))
hcols_2_lo=5
horizontal $hstart_2_lo $hrow_2_lo $hcols_2_lo "$char"

}

zero() {

set_color

hstart_0=$((f_st_cols_2 +4))
hcols_0=5
horizontal $hstart_0 $hrow_be $hcols_0 "$char"

str_dwn_col_0=$hstart_0
str_dwn_row_0=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_0 $str_dwn_row_0 "$char"

hstart_0_lo=$((f_st_cols_2 +4))
hcols_0_lo=6
hrow_0_lo=$((hrow_be+6))
horizontal $hstart_0 $hrow_0_lo $hcols_0 "$char"

str_dwn_col_rig_0=$((hstart_0 +5))
str_dwn_row_rig_0=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_rig_0 $str_dwn_row_rig_0 "$char"
}

one() {
set_color
str_dwn_col_1=$((str_dwn_col_rig_0 + 4))
str_dwn_row_1=$((hrow_be))
str_dwn 7 $str_dwn_col_1 $str_dwn_row_1 "$char"

}

nine() {
set_color

set_color

hstart_8=$((str_dwn_col_1 +4))
hcols_8=5
horizontal $hstart_8 $hrow_be $hcols_8 "$char"

str_dwn_col_8=$hstart_8
str_dwn_row_8=$((hrow_be + 1))
str_dwn 3 $str_dwn_col_8 $str_dwn_row_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+6))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

str_dwn_col_rig_8=$((hstart_8 +5))
str_dwn_row_rig_8=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_rig_8 $str_dwn_row_rig_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+3))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

}

six() {
set_color

set_color

hstart_8=$((str_dwn_col_1 +4))
hcols_8=5
horizontal $hstart_8 $hrow_be $hcols_8 "$char"

str_dwn_col_8=$hstart_8
str_dwn_row_8=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_8 $str_dwn_row_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+6))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

str_dwn_col_rig_8=$((hstart_8 +5))
str_dwn_row_rig_8=$((hrow_be + 1+3))
str_dwn 3 $str_dwn_col_rig_8 $str_dwn_row_rig_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+3))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

}

seven() {
set_color

hstart_7_top=$((str_dwn_col_1 +4))
hcols_7_top=4
hrow_7_top=$((hrow_be))
horizontal $hstart_7_top $hrow_7_top $hcols_7_top "$char"

hstart_7_mid=$((str_dwn_col_1+8))
hcols_7_mid=4
hrow_7_mid=$((hrow_be))
forward  $hrow_7_mid $hstart_7_mid  7 "$char" $color

}

eight() {
set_color

set_color

hstart_8=$((str_dwn_col_1 +4))
hcols_8=5
horizontal $hstart_8 $hrow_be $hcols_8 "$char"

str_dwn_col_8=$hstart_8
str_dwn_row_8=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_8 $str_dwn_row_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+6))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

str_dwn_col_rig_8=$((hstart_8 +5))
str_dwn_row_rig_8=$((hrow_be + 1))
str_dwn 6 $str_dwn_col_rig_8 $str_dwn_row_rig_8 "$char"

hstart_8_lo=$((f_st_cols_2 +4))
hcols_8_lo=6
hrow_8_lo=$((hrow_be+3))
horizontal $hstart_8 $hrow_8_lo $hcols_8 "$char"

}

set_color(){
color=$RANDOM 
color=$((color%6))
tput setaf $color
}

cols=`tput cols`
mid=$((cols/2))
start=$((mid-16))
#echo "What character do you want to use"
#read char
char="*"

tput clear
rows=5

begin_row=2
num_cols=6

two $start $begin_row $num_cols "$char" $color;zero;one;six
sleep 2
tput clear
two $start $begin_row $num_cols "$char" $color;zero;one;seven
sleep 2
tput clear
two $start $begin_row $num_cols "$char" $color;zero;one;eight
sleep 2
tput clear
two $start $begin_row $num_cols "$char" $color;zero;one;nine

tput setaf 7
tput cup 9 0

Run the script as

It should generate a countup from 2016,2017,2018 and 2019 on the terminal with random colors made up of *.

Making the changes in resolv.conf permanent

The previous post we modified resolv.conf to get the internet connectivity back. The problem with the solution is that the resolv.conf file gets overwritten on every boot. To make the changed dns name server permanent we the need to update the file

Update the contents of the file above with the line

Save the file and restart the networking

On the next reboot you should see the dns server nadded to the file resolv.conf.

wifi connected but No interent in ubuntu 18.04 after upgrade

After upgrade to ubutnu 18.04, the intenet connections both wired and wireless showed that they were connected but the internet was not working.

The issue turned to be wrong DNS server in /etc/resolv.conf

In the above resolv.conf file add the line

To change the resolv.conf open the file /etc/resolv.conf as root and add the abov line. Save the file and restart networking using

unable to launch vmplayer 14

After installing vmplayer 14 in ubuntu 18.04 player might fail to launch with vmmon modules failing to compile with errors

and

To get around these errors we will need to modify the code of vmmon as given in https://github.com/mkubecek/vmware-host-modules/commit/562121d7bc06 and https://github.com/mkubecek/vmware-host-modules/commit/770c7ffe611520ac96490d235399554c64e87d9f To do the above mentioend changes, you can follow the following steps. Go to the folder

Untar the folder vmmon.tar

This will create a folder vmmon-only which will contain the code for the module vmmon.Now we can follow the changes mentioned in the above two links in the respective files.

After doing the changes recreate the vmmon.tar using the following command

Now we should be able to launch vmplayer and the modules should get compiled successfully.

Basic Char driver for kernel version 4.15.0

In the post, Example Char driver, the code for a basic charchater driver is given along with the steps to insert it into the kernel and create a char device.

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h> // required for various structures related to files liked fops. 
#include <linux/uaccess.h> // required for copy_from and copy_to user functions 
#include <linux/semaphore.h>
#include <linux/cdev.h> 
static int Major;
dev_t dev_no,dev;
struct device1 {
 char array[100];
 struct semaphore sem;
}char_arr;

int open(struct inode *inode, struct file *filp)
{
 
 printk(KERN_INFO "Inside open \n");
 if(down_interruptible(&char_arr.sem)) {
  printk(KERN_INFO " could not hold semaphore");
  return -1;
 }
 return 0;
}

int release(struct inode *inode, struct file *filp) {
 printk (KERN_INFO "Inside close \n");
 printk(KERN_INFO "Releasing semaphore");
 up(&char_arr.sem);
 return 0;
}

ssize_t read(struct file *filp, char *buff, size_t count, loff_t *offp) {
 unsigned long ret;
 printk("Inside read \n");
 ret = copy_to_user(buff, char_arr.array, count);
 return ret;
}

ssize_t write(struct file *filp, const char *buff, size_t count, loff_t *offp) { 
 unsigned long ret;
 printk(KERN_INFO "Inside write \n");
 ret = copy_from_user(char_arr.array, buff, count);
 return count;
}

struct file_operations fops = {
 read:  read,
 write:  write,
 open:   open,
 release: release
};

struct cdev *kernel_cdev;

int char_arr_init (void) {
 int ret;

kernel_cdev = cdev_alloc(); 
  kernel_cdev->ops = &fops;
 kernel_cdev->owner = THIS_MODULE;
 printk (" Inside init module\n");
  ret = alloc_chrdev_region( &dev_no , 0, 1,"chr_arr_dev");
    if (ret < 0) {
  printk("Major number allocation is failed\n");
  return ret; 
 }
 
    Major = MAJOR(dev_no);
    dev = MKDEV(Major,0);
 sema_init(&char_arr.sem,1); 
 printk (" The major number for your device1 is %d\n", Major);
 ret = cdev_add( kernel_cdev,dev,1);
 if(ret < 0 )
 {
 printk(KERN_INFO "Unable to allocate cdev");
 return ret;
 }

return 0;
}

void char_arr_cleanup(void) {
 printk(KERN_INFO " Inside cleanup_module\n");
 cdev_del(kernel_cdev);
 unregister_chrdev_region(Major, 1);
}
MODULE_LICENSE("GPL"); 
module_init(char_arr_init);
module_exit(char_arr_cleanup);

The following is the updated code for the same driver tested for the kernel version 4.15.0.To test the working of the driver please use the code given in post User access for example driver

tar Cannot stat: No such file or directory

tar is a command used to create an archive for the folder to combine the contents of a folder into one archive. If we want to create an archive for the folder named xyz, as xyz.tar , running the command as shown below will throw an error

The problem is because of the wrong sequence of options being passed to the tar command. To get around the error the sequence of options to be passed is as below.

The above command will run with out errors and it should be able to create xyz.tar.

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