Basic Terminal commands

Terminals, also known as command lines or consoles. Using a terminal allows us to send simple text commands to our computer to do things.

1. grep

grep searches for PATTERNS in each FILE. grep prints each line that matches a pattern.

Syntax:

grep “text to search” file_name

To match the whole word

grep -w “text to search” file_name

To ignore case-sensitive

grep -i “text to search” file_name

To know the line number of matched text

grep -n “text to search” file_name

To include the required no of lines(4) after matched pattern

grep -A 4 “text to search” file_name

To include required no of lines(4) before matched pattern

grep -B 4 “text to search” file_name

To include required no of lines(4) before and after matched pattern

grep -C 4 “text to search” file_name

To search all files in current directry

grep “text to search” ./*

./*.txt –> will search all txt files

grep -r “text to search” . -> will search in subdirectories too

grep -rl “text to search” . -> will show the file names and directory only, not matching text

grep -rc “text to search” . -> will show the file names and directory with no of matching text

history | grep “text to search ” -> will show the history having searching text only

grep “…-…-….” Filename or grep -p “\d{3}-\d{3}-\d{4}”-> will show matching of “any 3 digit — any 3 digit — any 4 digit”

To check version

grep -v

2. curl

curl is a command line tool to transfer data to or from a server, using any of the supported protocols.

curl URL -> will show the response from the given URL

curl -i URL -> will show the response from the given URL with response header

curl -d ”key=value&key=value” URL -> to send an post request with data

curl -X PUT -d ”key=value&key=value” URL -> to send an PUT request

curl -X DELETE URL -> to send an DELETE request

curl -o filename.format URL -> to save response as a file

3. wget

The wget command is a command line utility for downloading files from the Internet.

wget URL -> will download the specific file

wget -r URL -> will download all files and sub folders too

wget -q URL -> to turn off output

4. tail

It prints the specified lines of the specified files.

tail filename -> will print last 10 lines

tail -n no.of_lines filename OR tail -no.of_lines filename

tail +from_line filename -> will print from the given(from_line) line

tail -q filename_1 filename_2 OR tail filename_1 filename_2 -> will print the lines from the given file

tail -f filename -> will print the last 10 lines and will update when the file is changed. (used for logfiles).

tail -v filename -> will print the filename in starting of text

tail — version -> to find the tail version

5. head

Head is also similar to tail. the tail will print the lines from bottom but the head will print the lines from the top.

for example, tail filename -> will print the first 10 lines of the given file

6. Less

less filename -> will show the file contents.

less -N filename -> to view the line numbers

7. Find

Used to find files and directories.

find directory -name filename

find directory -type d -> will search directories

find directory -type f -> will search files within given directory

find directory -type f -name “filename” -> will search the files based on given name in the given directories

find directory -type -iname “filename” -> will search the file with name case insensitive

find directory -type f -mmin -10 -> will show the files modified within 10 min ago

find directory -type f -mmin +10 -> will show the files modified more than 10 min ago

find directory -type f -mmin +1 -mmin -5 -> will sow the modified file more than 1 min and less than 5 min ago

find directory -type f -mtime -20 -> will show the modified files less than 20 days ago

find directory -size +5M -> will show the files over 5MB

find directory -perm 777 -> will show the files that have permission 777

find directory -type d -exec chmod 775 {} + -> will change mode (permission) of directories to 775. Where, exec -> execute the command.

find directory -type f -name “filename” -maxdepth 1 -> will show the files that match the given and within a directory of 1 (current directory).

8. ssh

ssh stands for “Secure Shell”. It is a protocol used to securely connect to a remote server/system.

ssh user_name@host (IP/Domain_name)

9. Kill

Kill is a built-in command which is used to terminate processes manually.

kill PID -> it will kill the process of the given PID. To get PIDs run the command ps