#+TITLE: bash commands
#+DATE: 2021-08-30
#+STARTUP: indent
#+OPTIONS: num:nil

* DONE work in bash tutorial
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  CLOCK: [2021-09-08 mié 18:52]--[2021-09-08 mié 19:22] =>  0:30
  CLOCK: [2021-09-04 sáb 16:04]--[2021-09-04 sáb 16:34] =>  0:30
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  :END:



* Execute stuffs


* Show command history

: history

The file can be found in the user home:

: /home/user/.bash_history




** Convert pdf to text or html using poppler

Use poppler and redirect the text to a org file.
~pdftotext~ converts a pdf to "txt" if no other format is
specified

: pdftotext foo.pdf foo

: pacman -S poppler
: pdftotext foo.pdf ->> foo.org # first option
: pdftotext foo.pdf foo.org # second option

Convert pdf to html

: pfdftohtml foo.pdf foo.html

** Convert files using pandoc

Use pandoc with "-s" flag to produce a standalone document and "-o" to
redirect output to a file.

In the example a file "foo" is converted from ~odt~ to ~org~

: pandoc -s -o foo.org foo.odt

** Convert files to pdf using libreoffice

Convert odt file "tcl_online3.odt" to pdf

: libreoffice --headless --convert-to pdf tcl_online3.odt



** Display files

Show content of a file. Concatenates and writes file.
Using "tac" reverses the result of "cat" command

: cat file.txt

Using head, tail and less to show parts of files

Showing the first two entries

#+begin_src bash
 head -n 2 /etc/hosts
#+end_src

  #+RESULTS:
  | 127.0.0.1 | localhost |
  | 127.0.1.1 | myuser    |

  Showing the last two entries

  #+begin_src bash
 tail -n 2 /etc/hosts
  #+end_src

  #+RESULTS:
  | ff02::1 | ip6-allnodes   |
  | ff02::2 | ip6-allrouters |


  #+begin_src bash
 less /etc/hosts
  #+end_src

  #+RESULTS:
  | 127.0.0.1 | localhost      |               |              |
  | 127.0.1.1 | myuser         |               |              |
  | ::1       | localhost      | ip6-localhost | ip6-loopback |
  | ff02::1   | ip6-allnodes   |               |              |
  | ff02::2   | ip6-allrouters |               |              |


Show content of a zip file using less and pipe "|"

#+begin_src bash
unzip -l tntvillage_484094.zip | less  
#+end_src

** Backup a file

  Using "cp"

  : cp bbdb{,.bak}

  : bbdb.bak

  Backups with tar (tape archiver)

  Back up of "home"

  * c = create file
  * v = verbose
  * f = write to a file/device
  * z = compress the file (gzip) "tar.bz"
  * j = compress the file (bzip2)

  : tar -czvf /tmp/home.tar.gz /home

** Simple code to encrypt

   Encrypt:

   : gpg -c X
   : gpg X

   Use the code to remove the original file:

   : shred --remove X


** Download files

This code download the file and the argument ~-O~ is to rename the file

#+begin_example
wget https://filetodownload.org -O new_file
#+end_example

* Devices

- mount /what /where
  - what = device name
  - where = directory
    - /mnt = devices that mount occasionally
    - /media = devices that mount frequently

: run/$USER/media/$LABEL

* List process

Use ~ps~, ~top~ or ~htop~ to list process:

 * ~ps~ reports a snapshot of the current process

: ps aux | less

 * ~top~ display dynamic real-time view of linux process

: top

 * ~htop~ displays an interactive process viewer

: htop

To kill a process use:

: kill [PID]

or

: pkill [PID]

PID = process identificator

* Evaluate time to load

In emacs:

: time emacs --eval '(save-buffers-kill-terminal)'

* Cool commands

: cal # calendar
: clear # clear output
: uname # display system information (-r, -p, -a)
: wc # wordcount (file name)
: date # check the date


* References:

 * [[https://wiki-dev.bash-hackers.org/][The bash hackers wiki]]
 * [[https://link.springer.com/content/pdf/bfm%3A978-1-4302-6829-1%2F1.pdf?error=cookies_not_supported&code=2e41714e-ca8f-4796-a077-3243c836ec90][Beginning the linux command line]]
 * [[https://pandoc.org/][Pandoc manual]]
 * [[https://stackoverflow.com/][stackoverflow]]