Shell-Scripting

Unix Shell Scripting; it provides you with an interface to the UNIX system

Different Type of Shells

• Bourne shell ( sh)
• Korn shell ( ksh)
• Bourne Again shell ( bash)
• POSIX shell ( sh)

Unix Shell commands are powerful tools used to interact with and manage the Unix operating system. They allow users to perform a wide range of tasks, from basic file manipulation to complex system administration. Here's a summary of key aspects and commonly used commands:

Navigation and Directory Management

ls: Lists files and directories. cd: Changes the current directory. pwd: Prints the current working directory. mkdir: Creates new directories. rmdir: Removes empty directories.

File Management

touch: Creates empty files or updates timestamps. cp: Copies files or directories. mv: Moves or renames files or directories. rm: Removes files or directories.

Viewing File Contents

cat: Concatenates and displays file contents. more and less: View file contents page by page. head: Displays the beginning of a file. tail: Displays the end of a file.

Searching and Filtering

grep: Searches for patterns within files. find: Searches for files in a directory hierarchy.

Permissions and Ownership

chmod: Changes file permissions. chown: Changes file ownership and group.

System Monitoring

ps: Displays current processes.

Miscellaneous

echo: Displays messages or variables. man: Displays the manual for other commands.

Open file data.txt in VI editor

vi data.txt

Find a linux capabilities using the below command

cat /usr/include/linux/capability.h 

Count Lines in a File

wc -l

Unix a tar.gx

tar -xvf data.tar.gz -C /opt/landingpad/stagingarea

List Mounts on the machine

df -kh 

ping a URL

ping github.com

Find all open connections and ports

netstat -tulpn 

Check network trace

traceroute github.com

Manipulating data using awk command - fetch selected columns from application log

awk '{print $1,$4}' app.log 

Split Large file into smaller files in Unix

split -b 1024K bigdata.psv segment

Encode text data to base64

echo  'someimportanttext' | base64

Decode base64 to text

echo  'c29tZWltcG9ydGFudHRleHQ=' | base64 --decode

MD5 Checksum

md5sum filename

Tail a file

tail -f data.txt 

Date

date +%H:%M 

Download a file from remote server

curl -O --silent ftp://<someserver>/data.zip

For 8 AM use 8, and for 8 PM use 20

30 08 10 06 * /home/jobs/run_backup.sh

• 30 – 30th Minute
• 08 – 08 AM
• 10 – 10th Day
• 06 – 6th Month (June)
• • – Every day of the week

Send Email

mail -s 'subject' -c 'cc-address' -b 'bcc-address' 'to-address'

Awk row 1 and 4

  awk '{print $1,$4}' data.txt 

Find longed line in data file using awk

awk '{ if (length($0) > max) max = length($0) } END { print max }' data.txt

egerp case insensitive search for data

egrep -i data filename | less 

Unix system information

uname 

Unix all system information

uname  -a

Difference between two files

diff A.dat B.dat

Kill a process

kill PID

or

kiil -9 PID

Links

https://math.mit.edu/services/help/new/unix