Lesson 06 - chad-p/wiki-linux-class GitHub Wiki

Bash Scripting

Site to check shell scripts

Alias

https://linuxize.com/post/how-to-create-bash-aliases/

Bash Scripting

echo “What is your favorite dish?”  
read dish
echo “I like $dish also!”

#!/bin/bash  
WHO_AM_I=$(whoami)  
LIST=`ls -a`  
echo $WHO_AM_I; echo $LIST

Logical Operators

AND = Please go to the store AND purchase some milk
OR = Please go to bed OR you will be grounded.

#!/bin/bash  
num=3  
read -ep "Enter a number: " userNum  
if [ $userNum -gt $num ]; then  
	echo "Your number is greater than the number in the variable"  
else  
	echo "The number in the variable is greater or equal to your number"  
fi

#!/bin/bash  
for i in {1..255};
do
    echo "i var is: $i"
done

#!/bin/bash  
# Clear file at the beginning of the process  
cd ~/Desktop  
echo "" > liveHost;  
# Loop in the range 1 to 255  
for i in {1..255};  
do  
    echo "[+] pinging 10.71.0.$i";  
    ping -c 1 10.71.0.$i | grep "bytes from" >> liveHost;  
done  
echo "Done!"

#!/bin/bash    
x=1  
#A loop that will run as long as the value of $x is less than 5  
while [ $x -lt 5 ]  
do  
    echo “Execution times count: $x”  
    x=$(( $x + 1 ))  
done

test 2 -gt 3; echo $?

#!/bin/bash  
touch /root/file.txt  
if [ $? -lt 1 ]  
then  
    echo “File created."  
else  
    echo “An error has occurred."  
fi

#!/bin/bash  
for i in {1..255};
do
    let sum=$i*$i
    echo "$i multiplied by itself equals: $sum"
done

Arithmetic

y=5 
x=10

let sum=2+2
echo "This is the sum $sum"  # This is the sum 4

let sum+=2
echo $sum

expr $x+$y # > 5+10
expr $x + $y # > 15
expr 5 * 5 # error because * needs to be \*
expr 11 / 5  # Still floor division

echo $x+$y  # > 5+10
echo $(($x+$y)) # > 15
echo $((x+y)) # > 15
echo $((x/y)) # > Floor result... Update x to 11 and rerun

expr $x+$y # > 5+10
expr $x + $y # > 15
expr 11 / 5  # Still floor division


echo "1 / 5" | bc
echo "scale=2; 11 / 5" | bc  # bc stands for basic calculator

Tar

https://www.interserver.net/tips/kb/use-tar-command-linux-examples/
https://catchchallenger.herman-brule.com/wiki/Quick_Benchmark:_Gzip_vs_Bzip2_vs_LZMA_vs_XZ_vs_LZ4_vs_LZO
- [c]reate an archive and write it to a [f]ile: tar cf target.tar file1 file2 file3
- [c]reate a g[z]ipped archive and write it to a [f]ile: tar czf target.tar.gz file1 file2 file3
- [c]reate a g[z]ipped archive from a directory using relative paths: tar czf target.tar.gz --directory=path/to/directory .
- E[x]tract a (compressed) archive [f]ile into the current directory [v]erbosely: tar xvf source.tar[.gz|.bz2|.xz]
- E[x]tract a (compressed) archive [f]ile into the target directory: tar xf source.tar[.gz|.bz2|.xz] --directory=directory
- [c]reate a compressed archive and write it to a [f]ile, using [a]rchive suffix to determine the compression program: tar caf target.tar.xz file1 file2 file3
- Lis[t] the contents of a tar [f]ile [v]erbosely: tar tvf source.tar
- E[x]tract files matching a pattern from an archive [f]ile: tar xf source.tar --wildcards "*.html"

bzip2/bunzip2 - A block-sorting file compressor.

Compress a file: bzip2 path/to/file_to_compress
Decompress a file: bzip2 -d path/to/compressed_file.bz2
Decompress a file to standard output: bzip2 -dc path/to/compressed_file.bz2

gzip

Compress a file, replacing it with a gzipped compressed version: gzip file.ext
Decompress a file, replacing it with the original uncompressed version: gzip -d file.ext.gz
Compress a file, keeping the original file: gzip --keep file.ext
Compress a file specifying the output filename: gzip -c file.ext > compressed_file.ext.gz
Decompress a gzipped file specifying the output filename: gzip -c -d file.ext.gz > uncompressed_file.ext
Specify the compression level. 1=Fastest (Worst), 9=Slowest (Best), Default level is 6: gzip -9 -c file.ext > compressed_file.ext.gz

zip

zip -e “locked.zip” file1 file2 file3 or --encrypt

Add files/directories to a specific archive: zip -r path/to/compressed.zip path/to/file_or_directory1 path/to/file_or_directory2 ...
Remove files/directories from a specific archive: zip --delete path/to/compressed.zip path/to/file_or_directory1 path/to/file_or_directory2 ...
Archive files/directories e[x]cluding specified ones: zip path/to/compressed.zip path/to/file_or_directory1 path/to/file_or_directory2 ... --exclude path/to/excluded_files_or_directories
Archive files/directories with a specific compression level (0 - the lowest, 9 - the highest): zip -r -0-9 path/to/compressed.zip path/to/file_or_directory1 path/to/file_or_directory2 ...
Create an encrypted archive with a specific password: zip -r --encrypt path/to/compressed.zip path/to/file_or_directory1 path/to/file_or_directory2 ...
Archive files/directories to a multi-part [s]plit zip file (e.g. 3 GB parts): zip -r -s 3g path/to/compressed.zip path/to/file_or_directory1 path/to/file_or_directory2 ...
Print a specific archive contents: zip -sf path/to/compressed.zip

xz

Compress a file to the xz file format: xz file
Decompress a xz file: xz -d file.xz
Compress a file to the LZMA file format: xz --format=lzma file
Decompress an LZMA file: xz -d --format=lzma file.lzma
Decompress a file and write to stdout: xz -dc file.xz
Compress a file, but don't delete the original: xz -k file
Compress a file using the fastest compression: xz -0 file
Compress a file using the best compression: xz -9 file

Hasing

Cron

https://crontab.guru