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Intro To Linux 10/15

In this document, we will run through some basic bash commands for file manipulation.

Prerequisites

For this workshop, we will be connecting to the CCIS machines, so it is necessary that you have your CCIS username and password.

  • Forgot your password? Go here

Windows Users:

  • Download PuTTY, an SSH client compatible with Windows
  • Open PuTTY > Host Name: "login.ccs.neu.edu" > Open
  • Enter your username and password

Mac/Linux Users:

  • In the terminal, ssh <username>@login.ccs.neu.edu
  • Enter your password

Terminal Commands

pwd

print working directory

Prints the full pathname of the current working directory

$ pwd
/home/lastname

ls

list

List all directories and files in the current working directory

$ ls
bin
classes
sample.txt

mkdir

make directory

Create a new empty directory

$ mkdir CoSMOWorkshop
$ ls
CoSMOWorkshop

cd

change directory

Move into the specified directory. Hint: use cd .. to move up to the parent directory

$ cd CoSMOWorkshop/
$ pwd
/home/lastname/CoSMOWorkshop/

echo

Sends arguments to standard out

$ echo "Hello World"
"Hello World"

Output from echo can be redirected to a file with >, eg: echo "making a test file" > sample.txt Output from echo can also be appended to a file with >>, eg: echo "second line" >> sample.txt

touch

Updates the timestamp of a file. Creates new, empty file if none exist

$ date -r sample.txt
Mon Oct 15 19:05:33 EDT 2018 
$ touch sample.txt
$ date -r sample.txt
Mon Oct 15 19:07:18 EDT 2018

cp

copy

Used to make a copy of a file, with a new name.

$ cp sample.txt copied.txt
$ ls
copied.txt sample.txt

mv

move

Used to move a file to a new location. Hint: can also be used to rename a file mv file.txt new_name.txt

$ mkdir cloned
$ mv copied.txt cloned/
$ cd cloned
$ ls
copied.txt

rm

remove

Used to remove a specified file. Hint: can be used to remove a directory by specifying rm directory --recursive

$ rm copied.txt
$ ls
$

nano

Used to edit files. Add changes, Ctrl+O to write those changes, Ctrl+X to exit.

$ nano sample.txt

vim

Another option for a text editor. Press i to insert. When finished, ESC and :wq to write and quit.

$ vim sample.txt

cat

concatenate

Concatenates multiple files and prints to standard output. Hint: cat is also used to print the output of a single file.

$ cat sample.txt
making a test file
second line

man

manual

Output the reference manual for a specific function

$ man echo
$ man grep > grep.txt

grep

global regular expression print

Search files for lines matching a specified pattern.

$ grep "count" grep.txt
    -c, --count
          ......

Grep has a ton of optional arguments, read the docs to see what they are!

$ grep -c "processor" /proc/cpuinfo
32

sed

stream editor

A powerful tool used to edit input streams, most commonly performing substitutions in text files.

$ echo "Linux is cool, I enjoy it." > test.txt
$ sed "s/Linux/CoSMO/" test.txt
CoSMO is cool, I enjoy it.

By default, sed will only edit the first match on each line, to edit the nth match, do sed "s/.../.../n". To edit ALL matches, sed "s/.../.../g

alias

Lets you assign a shorter name for a complicated (or simple) command

$ alias c='clear'
$ alias ..='cd ..'

To make these commands permanent, you need to add them to the ~/.bashrc file, otherwise they will disappear when you start a new session.

find

Used to find files/directories with certain characteristics

$ find . -name "*.txt
./grep.txt
./sample.txt
$ find . -type

xargs

extended arguments

Converts standard input into arguments for a command

$ ls | xargs cat

Helpful Notations

--help

Add this argument after a bash command to get helpful information about that command.

$ ls --help
Usage: ls [OPTION]... [FILE]...
.......

>

Used to redirect standard output to a new location.

echo "new text" > new_file.txt

>>

Appends standard output to a specified location.

echo "added text" > existing_file.txt

|

The pipe allows you to pass the output of the command on the left as input to the program on the right. Lets you chain together multiple commands.

find . -type f | xargs cat

$(...)

Allows for command substitution. Whatever is inside of the parentheses is evaluated, before the outer command is run.

echo "Today is $(date +"%m/%d/%Y")"