linux-cheat-sheet

my public linux cheat sheet containing some commands I might use & a short explanation of each one

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Contents List

Topic
Basic commands
File and strings

Basic commands

Basic commands notes

Command
pwd
ls
history
mkdir -p
rmdir
cat
cp
mv
rm

1. pwd shows your current directory

   $ pwd
   /home/mobin

2. ls lists files and directories

   $ ls
   HW  slides

there are different options for ls command:

   -t : sort by last modified (newest first)
   -l : more detailed
   $ ls -l
   total 4
   drwxrwxrwx 1 mobin mobin    0 Oct 11 16:41 HW
   drwxrwxrwx 1 mobin mobin 4096 Sep 30 10:14 slides

   -a : show everything including hidden
   -R : goes into every directory and recursively lists
   -h : shows memory section human readable (should be used with -l)

3. history shows previously executed commands

   $ history
   ...
   2203  ls
   2204  ls -l
   2205  history
   2206  pwd

4. mkdir -p creates parent directories recursively

   mkdir -p [new directory name]/[the insider directory name inside the new directory]

   $ mkdir -p d/inside-d
   $ ls -R
   .:
   d

   ./d:
   inside-d

   ./d/inside-d:

5. rmdir removes empty directories

   $ rmdir [directory1 name] [directory2 name] ...

we can force it to remove non-empty directories but it's more common to use rm -rf instead

rmdir -p: removes parent directories recursively

   $ rmdir -p d/inside-d/inside-inside-d

6. cat shows file's contents

   cat [file name]

   $ cat a.txt
   nothing special here

   -n : if you add this option, it shows files line numbers too

we can use this command to add to a file(using the option below everything we type will be saved in a.txt):

   $ cat > a.txt

7. cp copies file or directory to a destination path

copy file:

   cp [file you want to copy] [the path you want your file to be copied to and the name of it]

make a copy of a.txt in mydir named b.txt

   $ cp a.txt mydir/b.txt

copy directory:

we use -r option to copy directories along with their contents

   cp -r [directory you want to copy]/ [the path you want your directory to be copied to and the name of it]

make a copy of mydir1 to pdir named mydir2

   $ cp -r mydir1/ pdir/mydir2

8. mv cuts file or directory to a destination path, rename a file or directory

move file:

move a.txt to mydir directory

   $ mv a.txt mydir/

move directory:

move mydir1 directory to mydir2 directory

   $ mv mydir1/ mydir2/

rename:

rename a.txt to b.txt

   $ mv a.txt b.txt

9. rm removes file or directory

remove a.txt

   $ rm a.txt

remove a directory

   $ rm -r mydir/

Basic commands notes

1. ~ denotes a user's home directory

   $ cd ~
   $ pwd
   /home/mobin

2. use --help or man to get description of the command you need

3. there are 3 types of standard streams:

• standard input stream: source of input for the program
• standard output stream: used for output from the program
• standard error stream: used for error messages

4. pipelines are a kind of redirection in which we use to connect commands and get output from one and give it as input to another

   $ cat <<EOF | sort
   hello
   from
   alireza
   in quera
   to
   you
   EOF

   alireza
   from
   hello
   in quera
   to
   you

File and strings

File and strings notes

Command
du
file
find
head

1. du shows the space usage of files and directories of the current directory

   $ du
   680	    ./HWs/HW1
   680	    ./HWs
   32752	./slides/microcontroller_AVR
   16536	./slides/microprocessor
   49288	./slides
   230656   ./voices
   280624	.

as you can see, it recursively shows each directories space usage

we can pass the address to du too

there are some usefull options too:

   options:
   -h : shows space usage human readable
   -sh : just shows current direcotiry

2. file shows files type

   file [file name]

   $ file README.md
   README.md: ASCII text

3. find finds files and directories

   $ find [starting directory to search] -name "[file to search]"

   find . -name "*.txt"

4. head

File and strings notes

1. there are several editors in linux like vim & nano

   $ nano a.txt

   $ vim a.txt