I.01) Define two variables, var1=88 and var2=71. Print out (var1+var2), (var1*var2), (var1/var2), (var1%var2).
(Hint: try echoing $((var1+var2)) )
var1=88;var2=71;echo $((var1+var2))
var1=88;var2=71;echo $((var1*var2))
var1=88;var2=71;echo $((var1/var2))
var1=88;var2=71;echo $((var1%var2))
I.02) Add 2 to var2 and echo var2.
let var2+=2; echo $var2
I.03) Define two variables, var1=88.3 and var2=71. Print out var1+var2. What happened?
var1=88.3;var2=71;echo $((var1+var2))
#-bash: 88.3: syntax error: invalid arithmetic operator (error token is ".3")
I.04) An easy way to do floating point arithmetic in bash is to use bc command. Explore the use of bc and calculate var1+var2 if var1=88.3 and var2=73. Investigate the use of bc on the web or man/help pages.
echo "$var1+$var2" | bc
II.01) List the files with .so extension in “/lib64” folder to the libraries.txt file. Then, print out only the unique file names prior to “.so” to a file called “unique_libs.txt”.
ls /lib64 | grep -F .so > libraries.txt
cut -d. -f 1 libraries.txt | sort | uniq > unique_libs.txt
II.02) Split the unique_libs.txt to 4 files with more or less the same number of lines. The names of these split files should look like “splitlib_00”, “splitlib_01”, …
(Hint: Explore the use of split command but be careful to not to split an individual line between two files.)
split -d --number=l/4 unique_libs.txt splitlib_
II.03) Copy the file “splitlib_01” to “splitlib_01_1” but omit the first three lines of “splitlib_01”.
(Hint: You can do this with tail command.)
tail -n +4 splitlib_01 > splitlib_01_1
II.04) Combine “splitlib_00”, “splitlib_01_1”, “splitlib_02” and “splitlib_03” to create “unique_libs_defected.txt”. “unique_libs.txt” and “unique_libs_defected.txt” should be same except the missing 3 lines.
cat splitlib_00 splitlib_01_1 splitlib_02 splitlib_03 > unique_libs_defected.txt
#or
cat splitlib_0* > unique_libs_defected.txt
II.05) Identify the names of the missing library names in “unique_libs_defected.txt” and their line numbers in “unique_libs.txt”.
(Hint: Explore diff command)
diff unique_libs.txt unique_libs_defected.txt
II.06) Combine “splitlib_00” and “splitlib_01” into “pasted_libs.txt” which will include 2 columns: the library names from “splitlib_00” in the first column and library names from “splitlib_01” in the second column. The columns should be separated by comma. Do you have two columns in every line?
(Hint: Explore paste command.)
paste -d, splitlib_00 splitlib_01 > pasted_libs.txt
II.07) Print out “splitlib_00” file in reverse order (i.e. bottom to top).
(Hint: You can use cat command to print a file from top to bottom to the screen. What command could do the reverse?)
tac splitlib_00
II.08) List everything in your current working directory according to their modifictation time.
ls -t
II.09) List only the files in your current directory and any directories within with respect to their sizes.
(Hint: By combining find and xargs commands you can do this easily. Explore how to use xargs command.)
find . -type f | xargs ls -lS
II.10) Make four new folders (“slib_00”, “slib_01”, …) and move “splitlib_00” to “slib_00” folder, move “splitlib_01” to “slib_01” folder, and so on.
echo slib_00 slib_01 slib_02 slib_03 | xargs mkdir
#or
for i in 00 01 02 03; do mv splitlib_$i ./slib_$i; done
II.11) Combining find, xargs and grep commands search for ‘python’ string in files with sizes greater than 1 kilobytes in the current working folder and all the folders within.
find . -size +1k -type f | xargs grep 'python'
II.12) Find all the files in “/lib64” folder which are larger than 4 Megabytes and show their sizes. Do not let find to search files at deeper levels in “/lib64” folder hierarchy.
find /lib64/ -maxdepth 1 -size +2M -type f -ls
III.01) Write a loop command to print out integers 1 to 20 (increasing order) to the screen where each number should be printed out on a separate line.
for ((i=1;i<=20;i+=1)); do echo $i; done
#or
for i in `seq 20`; do echo $i; done
III.02) Write a loop command to print out integers 20 to 1 in (decreasing order) to the screen where each number should be printed out on a separate line.
for ((i=20;i>0;i-=1)); do echo $i; done
III.03) In addition to for, loops can be created with while statement in bash scripts. Using while loop repeat the last twp exercises i.e.:
while, the loop continues until some condition is false. The argument of the condition should change during the loop operation. Otherwise you would end up with an infinite loop. Explore while loops on the web for further details.)i=1; while [ $i -lt 21 ]; do echo $i; i=$((i+1)); done
i=20; while [ $i -gt 0 ]; do echo $i; i=$((i-1)); done
III.04) Write a loop command to print out integers 20 to 1 in (decreasing order) to the screen where all the numbers printed on the same line separated with a space.
for ((i=20;i>0;i-=1)); do echo -n "$i "; done; echo " "
III.05) Write a loop command to print out integers 1 to 20 (increasing order) to a file (called “integers.txt”) where each number should be printed out on a separate line.
rm integers.txt; touch integers.txt; for ((i=1;i<=20;i+=1)); do echo $i>> integers.txt; done
III.06) Write a command including a loop to add 1 to each integer in “integers.txt” file and write it to “plusone.txt”. Assume you don’t know the number of lines in “integer.txt”.
rm plusone.txt
i=`cat integers.txt | wc -l`
touch plusone.txt
for j in `seq $i`; do l=`head -n $j integers.txt | tail -1`; echo $((l+1))>>plusone.txt; done
III.07) Do the same as operation in the last question but this time use sed function witin the loop to access each line in “integers.txt”. Search for sed function on the web or read man sed or sed --help for its use. Again, assume you don’t know the number of lines in “integer.txt”.
rm plusone.txt
i=`cat integers.txt | wc -l`
touch plusone.txt
for j in `seq $i`; do l=`sed -n "$j"p integers.txt`; echo $((l+1))>>plusone.txt; done
III.08) Write a loop to create 100 folders with names “1”,”2”,”3”,…,”100”. Echo which folder is created each step. Use seq function to identify the values over which the loop iterates. Search for seq function on the web or read man seq or seq --help.
for i in `seq 100`; do mkdir $i; echo $i; done
III.09) Delete the 100 folders using a similar loop as the last question.
for i in `seq 100`; do rm -Rf $i; done
III.10) Write a loop to create 100 folders with names “001”, “002”,…,”100”. Echo which folder is created each step. Again, use seq function to identify the values over which the loop iterates. Search for seq function on the web or read man seq or seq --help.
(Hint: Read flags of seq function.)
for i in `seq -w 100`; do mkdir $i; done
III.11) Delete the 100 folders using created in the last question.
for i in `seq -w 100`; do rm -Rf $i; done
III.12) Write a loop to create 10 folders with names “1”, “2”,…,”10” but after a folder is created make the code to wait for 3 seconds before creating another folder. Echo which folder is created each step.
for i in `seq 10`; do mkdir $i; echo $i; sleep 3; done
IV.01) Print your name the one million times (each on one line) along with the line number to the file “ilikemyname.txt”. Use VIM text editor to open “ilikemyname.txt” and delete 783219th line.
rm ilikemyname.txt
touch ilikemyname.txt
for i in `seq 1000000`; do echo "Alper Kinaci" $i >> ilikemyname.txt; done
vim ilikemyname.txt
#-- Go to the command-line mode (hit "esc" then ":"), two alternatives after that:
#1- write 783219 and hit enter/return,
#2- write ?783219 and hit enter/return. Hit d two times
IV.02) While you are viewing ilikemyname.txt with VIM, set VIM to show line numbers.
#-- Go to the command-line mode (hit "esc" then ":") and write set nu, hit enter/return
IV.03) Undo your deletion.
#-- Hit "esc" to go to the normal mode and hit "u"
IV.04) Only erase the number after your name on line 783219.
#-- Again you have many options here:
#1- Hit "esc" to switch to the normal mode, move the cursor to the beginning of the
#number and hit "x" 6 times to erase the number on that line one character at a time
#or
#1- Hit "esc" and "6" and then "x" to erase 6 characters. There are several more ways.
IV.05) While viewing ilikemyname.txt with VIM editor, go to the last line and enter the text “Last” before your name. Then go to the first line of the file and enter the text “First” after your name.
#-- Follow the steps below
#1- Hit "esc" and ":" to go to the command-line mode
#2- Write "$", hit enter/return
#3- Hit "i" to enter insert mode and type "Last" before your name
#4- Hit "esc" and ":" to go to the command-line mode
#5- Write "0", hit enter/return
#6- Hit "i" to enter insert mode, move the cursor after your name and type "First"
IV.06) Save the file, then save the file as “ilikemayname_bckp.txt” and quit to command line.
#-- Follow the steps below:
#1- Hit "esc" and ":" to go to the command-line mode
#2- Write "w", hit enter/return. The file is saved
#3- Hit "esc" and ":" to go to the command-line mode
#4- Write "w ilikemayname_bckp.txt", hit enter/return. You created ilikemayname_bckp.txt
#5- Hit "esc" and ":" to go to the command-line mode
#6- Write "wq", hit enter/return to save and quit
IV.07) Open “ilikemyname.txt” and “ilikemayname_bckp.txt” both in a single VIM window side-by-side. Delete the first 134000 lines in “ilikemyname.txt”. Delete your name in all lines of “ilikemayname_bckp.txt”
vim -O ilikemyname.txt ilikemayname_bckp.txt
#-- The command above will open 2 files in one VIM editor window. Now, follow the step below:
#1- Make sure the cursor is on ilikemyname.txt tab
#2- Hit "esc" to go to normal mode
#3- Write 134000 and hit "d" 2 times. 134K lines deleted
#4- To move the cursor to ilikemayname_bckp.txt tab hit "esc" (normal mode) and do "Ctrl+w" and hit "w" again.
#5- Hit "esc" and ":" to go to the command-line mode
#6- Write %s/Your Name//g, hit enter/return. All your names are deleted from ilikemayname_bckp.txt tab
#7- Hit "esc" and ":" to go to the command-line mode
#8- Write "wq", hit enter/return to save and quit rom ilikemayname_bckp.txt tab
#9- Hit "esc" and ":" to go to the command-line mode
#10- Write "wq", hit enter/return to save and quit
IV.08) You can work with VIM without opening the editor window. This is called batch mode. Copy ilikemyname.txt” to “ilikemayname_bckp.txt”. Now both files have your name. Delete your name in all lines of “ilikemayname_bckp.txt” and save the file with VIM without opening editor window.
(Hint: Explore vim -c ... i.e. -c flag)
cp ilikemyname.txt ilikemayname_bckp.txt
vim -c ":%s/Your Name//g" -c ":wq" ilikemayname_bckp.txt
V.01) Write a script to find if a file exists in “/lib64”. Input the filename as a parameter and if the file is in the folder, the script should print out “yourfilename file exists”. Otherwise the script should print out “yourfilename file does not exits”
#!/usr/bin/env bash
filename=$1
if [ -f /lib64/$filename ]; then
echo "$filename" 'file exits'
else
echo "$filename" 'file does not exist'
V.02) Write a bash script which outputs:
#!/usr/bin/env bash
myflag="$1"
if [ $myflag -eq 1 ]; then
echo 'True'
elif [ $myflag -eq 0 ]; then
echo 'False'
else
echo 'Enter 0 or 1'
fi
V.03) Write a bash script to generate 1000 random numbers between 1 and 1000 and write them to a file. Find out how many unique numbers are obtained.
(Hint: Try issuing echo $RANDOM, what do you get?)
#!/usr/bin/env bash
rm randomnumbers.txt
touch randomnumbers.txt
for i in `seq 1000`
do
echo $(((RANDOM%1000)+1)) >> randomnumbers.txt
done
sort -n randomnumbers.txt | uniq | wc -l
V.04) Write a script to run the script you have developed for unique random numbers n times. n is a variable parameter you will set as an input when you are starting your script.
#!/usr/bin/env bash
for j in `seq $1`; do
rm randomnumbers.txt
touch randomnumbers.txt
for i in `seq 1000`; do
echo $(((RANDOM%1000)+1)) >> randomnumbers.txt
done
sort -n randomnumbers.txt | uniq | wc -l
done