MKT615: Data Storytelling for Marketers

class: center, middle, inverse, title-slide

# MKT615: Data Storytelling for Marketers
## Lecture 3: The Shell
### Davide Proserpio
### Marshall School of Business

---

# Table of contents

1. [Introduction](#intro)

2. [Bash shell basics](#basics)

3. [SSH](#remote)

3. [Files and directories](#files)

4. [Working with text files](#text)

5. [Redirecting and pipes](#pipes)

6. [Scripting](#scripting)

7. [User roles and file permissions](#permissions)

8. [Changing permissions](#permissions2)

9. [Vim, running scripts, and monitor resources](#vim)

10. [Appendix (Windows users only)](#windows)

---

name:start
# Checklist

☑ Have you cloned the [course repo](https://github.com/dadepro/mkt-615) to your local machine?

☑ Do you have Bash-compatible shell? You should be ok with Mac and Linux, **Windows** users: see [here](#windows) before continuing (or you can decide to use **mshresearch** and [RStudio Server](http://mshresearch.marshall.usc.edu:8787/) ready for your to use)

</br>

(This lecture is the last detour before we get back to data analyis with R and RStudio.)

---
class: inverse, center, middle
name: intro

# Introduction

---

# Definitions

Don't be thrown off by terminology: *shell*, *terminal*, *tty*, *command prompt*, etc. 
- These are all basically just different names for the same thing.<sup>1</sup>
- They are all referring to a **Command Line Interface** (CLI).

.footnote[
<sup>1</sup> [Truth be told](https://unix.stackexchange.com/questions/4126/what-is-the-exact-difference-between-a-terminal-a-shell-a-tty-and-a-con), there are some subtle and sometimes important differences, as well as some interesting history behind the names. But we can safely ignore these here.
]

There are many shell variants, but we're going to focus on [**Bash**](https://www.gnu.org/software/bash/) (i.e. **B**ourne **a**gain **sh**ell).
- Included by default on Linux and MacOS.
- Windows users need to install a Bash-compatible shell first (again, see [here](#windows)).

(For the record, MacOS default shell is now [zsh](https://ohmyz.sh/) (i.e. the "Z shell"). As a result, my shell might look slightly different to yours during live coding sessions. The commands will stay the same, though.)

---

# Why even bother with the shell?

1. Power
  - Both for executing commands and for fixing problems. There are some things you just can't do in an IDE or GUI.

2. Reproducibility
 - Scripting is reproducible, while clicking is not.

3. Interacting with servers and high-performance computers
  - The shell is often the only option for high performance computing.

4. Automating workflow and analysis pipelines
  - Easily track and reproduce an entire project (e.g. use a Makefile to combine multiple programs, scripts, etc.)

---
# What do I use the shell for?

- Git/SVN

- Running scripts (Python, Bash scripts, R, etc.)

- Managing mshresearch (creating users, monitoring resources, etc.)

- Installing software

- Schedule tasks ([Crontab](https://crontab.guru/))

- File management (renaming, moving, etc.)

- Probably more things I am forgetting about

---
class: inverse, center, middle
name: basics

# Bash shell basics

---

# First look

Let's open up our Bash shell.

- [Linux](https://www.wikihow.com/Open-a-Terminal-Window-in-Ubuntu)
- [Mac](https://www.techwalla.com/articles/how-to-open-terminal-on-a-macbook)
- [Windows](https://www.howtogeek.com/265900/everything-you-can-do-with-windows-10s-new-bash-shell/)

You can also use RStudio if you prefer:
- [RStudio's built-in Terminal](https://support.rstudio.com/hc/en-us/articles/115010737148-Using-the-RStudio-Terminal).

---

# First look (cont.)

You should see something like:

```bash
 username@hostname:~$
```

This is shell-speak for: "Who am I and where am I?"0

- `username` denotes a specific user (one of potentially many on this computer).

- `@hostname` denotes the name of the computer or server.

- `:~` denotes the directory path (where `~` signifies the user's home directory).

- `$` denotes the start of the command prompt.
  - We'll get to this later, but for a special "superuser" called root, the dollar sign will change to a `#`.

---

# Useful keyboard shortcuts

- `Tab` completion.

- Use the `↑` (and `↓`) keys to scroll through previous commands.

- `Ctrl`+`→` (and `Ctrl`+`←`) to skip whole words at a time.

- `Ctrl`+`a` moves the cursor to the beginning of the line.

- `Ctrl`+`e` moves the cursor to the end of the line.

- `Ctrl`+`k` deletes everything to the right of the cursor.

- `Ctrl`+`u` deletes everything to the left of the cursor.

- `Alt`+`Del` delete a word to the left (`option` for Mac)

- `Ctrl`+`Shift`+`c` to copy and `Ctrl`+`Shift`+`v` to paste (I think `shift` is optional if you are not using RStudio shell)

- `clear` to clear your terminal.

---

# Syntax

All Bash commands have the same basic syntax:

**<center>command option(s) argument(s)</center>**

Examples:

```bash
  $ ls -lh ~/Documents/
  ```
  ```bash
  $ sort -u myfile.txt
  ```

---
count: false

# Syntax

All Bash commands have the same basic syntax:

**<center><span style='background: #ffff88;'>command</span> option(s) argument(s)</center>**

Examples:

```bash
  $ `ls` -lh ~/Documents/
  ```
  ```bash
  $ `sort` -u myfile.txt
  ```

---
count: false

# Syntax

All Bash commands have the same basic syntax:

**<center>command <span style='background: #ffff88;'>option(s)</span> argument(s)</center>**

Examples:

```bash
  $ ls `-lh` ~/Documents/
  ```
  ```bash
  $ sort `-u` myfile.txt
  ```

---
count: false

# Syntax

All Bash commands have the same basic syntax:

**<center>command option(s) <span style='background: #ffff88;'>argument(s)</span></center>**

Examples:

```bash
  $ ls -lh `~/Documents/`
  ```
  ```bash
  $ sort -u `myfile.txt`
  ```

---

# Syntax

All Bash commands have the same basic syntax:

**<center>command option(s) argument(s)</center>**

Examples:

```bash
  $ ls -lh ~/Documents/
  ```
  ```bash
  $ sort -u myfile.txt
  ```

</br>

**Commands**
- You don't always need options or arguments. (E.g. `$ ls ~/Documents/` and `$ ls -lh` are both valid commands that will yield output.)
- However, you always need a command.

---

# Syntax (cont.)

**options** (also called **flags**)
- Start with a dash.
- Usually one letter.
- Multiple options can be chained together under a single dash.
  ```bash
  $ ls -l -a -h /var/log ## This works
  $ ls -lah /var/log ## So does this
  ```
- An exception is with (rarer) options requiring two dashes.
  ```bash
  $ ls --group-directories-first --human-readable /var/log
  ```

**arguments**
- Tell the command *what* to operate on.
- Usually a file, path, or a set of files and folders.

---

# Help: man

The `man` command ("manual pages") is your friend if you ever need help.
- Tip: Hit spacebar to scroll down a page at a time, "h" to see the help notes of the `man` command itself and "q" to quit.

```bash
man ls
```

```
## 
## LS(1)                     BSD General Commands Manual                    LS(1)
## 
## NNAAMMEE
##      llss -- list directory contents
## 
## SSYYNNOOPPSSIISS
##      llss [--AABBCCFFGGHHLLOOPPRRSSTTUUWW@@aabbccddeeffgghhiikkllmmnnooppqqrrssttuuwwxx11%%] [_f_i_l_e _._._.]
## 
## DDEESSCCRRIIPPTTIIOONN
##      For each operand that names a _f_i_l_e of a type other than directory, llss
##      displays its name as well as any requested, associated information.  For
##      each operand that names a _f_i_l_e of type directory, llss displays the names
##      of files contained within that directory, as well as any requested, asso-
##      ciated information.
## 
##      If no operands are given, the contents of the current directory are dis-
##      played.  If more than one operand is given, non-directory operands are
##      displayed first; directory and non-directory operands are sorted sepa-
##      rately and in lexicographical order.
## 
##      The following options are available:
## 
##      --@@      Display extended attribute keys and sizes in long (--ll) output.
## 
##      --11      (The numeric digit ``one''.)  Force output to be one entry per
##              line.  This is the default when output is not to a terminal.
## 
##      --AA      List all entries except for _. and _._..  Always set for the super-
##              user.
## 
##      --aa      Include directory entries whose names begin with a dot (_.).
## 
##      --BB      Force printing of non-printable characters (as defined by
##              ctype(3) and current locale settings) in file names as \_x_x_x,
##              where _x_x_x is the numeric value of the character in octal.
## 
##      --bb      As --BB, but use C escape codes whenever possible.
## 
##      --CC      Force multi-column output; this is the default when output is to
##              a terminal.
## 
##      --cc      Use time when file status was last changed for sorting (--tt) or
##              long printing (--ll).
## 
##      --dd      Directories are listed as plain files (not searched recursively).
## 
##      --ee      Print the Access Control List (ACL) associated with the file, if
##              present, in long (--ll) output.
## 
##      --FF      Display a slash (`/') immediately after each pathname that is a
##              directory, an asterisk (`*') after each that is executable, an at
##              sign (`@') after each symbolic link, an equals sign (`=') after
##              each socket, a percent sign (`%') after each whiteout, and a ver-
##              tical bar (`|') after each that is a FIFO.
## 
##      --ff      Output is not sorted.  This option turns on the --aa option.
## 
##      --GG      Enable colorized output.  This option is equivalent to defining
##              CLICOLOR in the environment.  (See below.)
## 
##      --gg      This option is only available for compatibility with POSIX; it is
##              used to display the group name in the long (--ll) format output
##              (the owner name is suppressed).
## 
##      --HH      Symbolic links on the command line are followed.  This option is
##              assumed if none of the --FF, --dd, or --ll options are specified.
## 
##      --hh      When used with the --ll option, use unit suffixes: Byte, Kilobyte,
##              Megabyte, Gigabyte, Terabyte and Petabyte in order to reduce the
##              number of digits to three or less using base 2 for sizes.
## 
##      --ii      For each file, print the file's file serial number (inode num-
##              ber).
## 
##      --kk      If the --ss option is specified, print the file size allocation in
##              kilobytes, not blocks.  This option overrides the environment
##              variable BLOCKSIZE.
## 
##      --LL      Follow all symbolic links to final target and list the file or
##              directory the link references rather than the link itself.  This
##              option cancels the --PP option.
## 
##      --ll      (The lowercase letter ``ell''.)  List in long format.  (See
##              below.)  A total sum for all the file sizes is output on a line
##              before the long listing.
## 
##      --mm      Stream output format; list files across the page, separated by
##              commas.
## 
##      --nn      Display user and group IDs numerically, rather than converting to
##              a user or group name in a long (--ll) output.  This option turns on
##              the --ll option.
## 
##      --OO      Include the file flags in a long (--ll) output.
## 
##      --oo      List in long format, but omit the group id.
## 
##      --PP      If argument is a symbolic link, list the link itself rather than
##              the object the link references.  This option cancels the --HH and
##              --LL options.
## 
##      --pp      Write a slash (`/') after each filename if that file is a direc-
##              tory.
## 
##      --qq      Force printing of non-graphic characters in file names as the
##              character `?'; this is the default when output is to a terminal.
## 
##      --RR      Recursively list subdirectories encountered.
## 
##      --rr      Reverse the order of the sort to get reverse lexicographical
##              order or the oldest entries first (or largest files last, if com-
##              bined with sort by size
## 
##      --SS      Sort files by size
## 
##      --ss      Display the number of file system blocks actually used by each
##              file, in units of 512 bytes, where partial units are rounded up
##              to the next integer value.  If the output is to a terminal, a
##              total sum for all the file sizes is output on a line before the
##              listing.  The environment variable BLOCKSIZE overrides the unit
##              size of 512 bytes.
## 
##      --TT      When used with the --ll (lowercase letter ``ell'') option, display
##              complete time information for the file, including month, day,
##              hour, minute, second, and year.
## 
##      --tt      Sort by time modified (most recently modified first) before sort-
##              ing the operands by lexicographical order.
## 
##      --uu      Use time of last access, instead of last modification of the file
##              for sorting (--tt) or long printing (--ll).
## 
##      --UU      Use time of file creation, instead of last modification for sort-
##              ing (--tt) or long output (--ll).
## 
##      --vv      Force unedited printing of non-graphic characters; this is the
##              default when output is not to a terminal.
## 
##      --WW      Display whiteouts when scanning directories.  (--SS) flag).
## 
##      --ww      Force raw printing of non-printable characters.  This is the
##              default when output is not to a terminal.
## 
##      --xx      The same as --CC, except that the multi-column output is produced
##              with entries sorted across, rather than down, the columns.
## 
##      --%%      Distinguish dataless files and directories with a '%' character
##              in long (--ll) output, and don't materialize dataless directories
##              when listing them.
## 
##      The --11, --CC, --xx, and --ll options all override each other; the last one
##      specified determines the format used.
## 
##      The --cc and --uu options override each other; the last one specified deter-
##      mines the file time used.
## 
##      The --BB, --bb, --ww, and --qq options all override each other; the last one
##      specified determines the format used for non-printable characters.
## 
##      The --HH, --LL and --PP options all override each other (either partially or
##      fully); they are applied in the order specified.
## 
##      By default, llss lists one entry per line to standard output; the excep-
##      tions are to terminals or when the --CC or --xx options are specified.
## 
##      File information is displayed with one or more <blank>s separating the
##      information associated with the --ii, --ss, and --ll options.
## 
##    TThhee LLoonngg FFoorrmmaatt
##      If the --ll option is given, the following information is displayed for
##      each file: file mode, number of links, owner name, group name, number of
##      bytes in the file, abbreviated month, day-of-month file was last modi-
##      fied, hour file last modified, minute file last modified, and the path-
##      name.  In addition, for each directory whose contents are displayed, the
##      total number of 512-byte blocks used by the files in the directory is
##      displayed on a line by itself, immediately before the information for the
##      files in the directory.  If the file or directory has extended
##      attributes, the permissions field printed by the --ll option is followed by
##      a '@' character.  Otherwise, if the file or directory has extended secu-
##      rity information (such as an access control list), the permissions field
##      printed by the --ll option is followed by a '+' character.  If the --%%
##      option is given, a '%' character follows the permissions field for data-
##      less files and directories, possibly replacing the '@' or '+' character.
## 
##      If the modification time of the file is more than 6 months in the past or
##      future, then the year of the last modification is displayed in place of
##      the hour and minute fields.
## 
##      If the owner or group names are not a known user or group name, or the --nn
##      option is given, the numeric ID's are displayed.
## 
##      If the file is a character special or block special file, the major and
##      minor device numbers for the file are displayed in the size field.  If
##      the file is a symbolic link, the pathname of the linked-to file is pre-
##      ceded by ``->''.
## 
##      The file mode printed under the --ll option consists of the entry type,
##      owner permissions, and group permissions.  The entry type character
##      describes the type of file, as follows:
## 
##            bb     Block special file.
##            cc     Character special file.
##            dd     Directory.
##            ll     Symbolic link.
##            ss     Socket link.
##            pp     FIFO.
##            --     Regular file.
## 
##      The next three fields are three characters each: owner permissions, group
##      permissions, and other permissions.  Each field has three character posi-
##      tions:
## 
##            1.   If rr, the file is readable; if --, it is not readable.
## 
##            2.   If ww, the file is writable; if --, it is not writable.
## 
##            3.   The first of the following that applies:
## 
##                       SS     If in the owner permissions, the file is not exe-
##                             cutable and set-user-ID mode is set.  If in the
##                             group permissions, the file is not executable and
##                             set-group-ID mode is set.
## 
##                       ss     If in the owner permissions, the file is exe-
##                             cutable and set-user-ID mode is set.  If in the
##                             group permissions, the file is executable and set-
##                             group-ID mode is set.
## 
##                       xx     The file is executable or the directory is search-
##                             able.
## 
##                       --     The file is neither readable, writable, exe-
##                             cutable, nor set-user-ID nor set-group-ID mode,
##                             nor sticky.  (See below.)
## 
##                 These next two apply only to the third character in the last
##                 group (other permissions).
## 
##                       TT     The sticky bit is set (mode 1000), but not execute
##                             or search permission.  (See chmod(1) or
##                             sticky(8).)
## 
##                       tt     The sticky bit is set (mode 1000), and is search-
##                             able or executable.  (See chmod(1) or sticky(8).)
## 
## EEXXAAMMPPLLEESS
##      The following is how to do an llss listing sorted by increasing size
## 
##            ls -lrS
## 
## DDIIAAGGNNOOSSTTIICCSS
##      The llss utility exits 0 on success, and >0 if an error occurs.
## 
## EENNVVIIRROONNMMEENNTT
##      The following environment variables affect the execution of llss:
## 
##      BLOCKSIZE       If the environment variable BLOCKSIZE is set, the block
##                      counts (see --ss) will be displayed in units of that size
##                      block.
## 
##      CLICOLOR        Use ANSI color sequences to distinguish file types.  See
##                      LSCOLORS below.  In addition to the file types mentioned
##                      in the --FF option some extra attributes (setuid bit set,
##                      etc.) are also displayed.  The colorization is dependent
##                      on a terminal type with the proper termcap(5) capabili-
##                      ties.  The default ``cons25'' console has the proper
##                      capabilities, but to display the colors in an xterm(1),
##                      for example, the TERM variable must be set to
##                      ``xterm-color''.  Other terminal types may require simi-
##                      lar adjustments.  Colorization is silently disabled if
##                      the output isn't directed to a terminal unless the
##                      CLICOLOR_FORCE variable is defined.
## 
##      CLICOLOR_FORCE  Color sequences are normally disabled if the output isn't
##                      directed to a terminal.  This can be overridden by set-
##                      ting this flag.  The TERM variable still needs to refer-
##                      ence a color capable terminal however otherwise it is not
##                      possible to determine which color sequences to use.
## 
##      COLUMNS         If this variable contains a string representing a decimal
##                      integer, it is used as the column position width for dis-
##                      playing multiple-text-column output.  The llss utility cal-
##                      culates how many pathname text columns to display based
##                      on the width provided.  (See --CC and --xx.)
## 
##      LANG            The locale to use when determining the order of day and
##                      month in the long --ll format output.  See environ(7) for
##                      more information.
## 
##      LSCOLORS        The value of this variable describes what color to use
##                      for which attribute when colors are enabled with
##                      CLICOLOR.  This string is a concatenation of pairs of the
##                      format _f_b, where _f is the foreground color and _b is the
##                      background color.
## 
##                      The color designators are as follows:
## 
##                            aa     black
##                            bb     red
##                            cc     green
##                            dd     brown
##                            ee     blue
##                            ff     magenta
##                            gg     cyan
##                            hh     light grey
##                            AA     bold black, usually shows up as dark grey
##                            BB     bold red
##                            CC     bold green
##                            DD     bold brown, usually shows up as yellow
##                            EE     bold blue
##                            FF     bold magenta
##                            GG     bold cyan
##                            HH     bold light grey; looks like bright white
##                            xx     default foreground or background
## 
##                      Note that the above are standard ANSI colors.  The actual
##                      display may differ depending on the color capabilities of
##                      the terminal in use.
## 
##                      The order of the attributes are as follows:
## 
##                            1.   directory
##                            2.   symbolic link
##                            3.   socket
##                            4.   pipe
##                            5.   executable
##                            6.   block special
##                            7.   character special
##                            8.   executable with setuid bit set
##                            9.   executable with setgid bit set
##                            10.  directory writable to others, with sticky bit
##                            11.  directory writable to others, without sticky
##                                 bit
## 
##                      The default is "exfxcxdxbxegedabagacad", i.e. blue fore-
##                      ground and default background for regular directories,
##                      black foreground and red background for setuid executa-
##                      bles, etc.
## 
##      LS_COLWIDTHS    If this variable is set, it is considered to be a colon-
##                      delimited list of minimum column widths.  Unreasonable
##                      and insufficient widths are ignored (thus zero signifies
##                      a dynamically sized column).  Not all columns have
##                      changeable widths.  The fields are, in order: inode,
##                      block count, number of links, user name, group name,
##                      flags, file size, file name.
## 
##      TERM            The CLICOLOR functionality depends on a terminal type
##                      with color capabilities.
## 
##      TZ              The timezone to use when displaying dates.  See
##                      environ(7) for more information.
## 
## CCOOMMPPAATTIIBBIILLIITTYY
##      The group field is now automatically included in the long listing for
##      files in order to be compatible with the IEEE Std 1003.2 (``POSIX.2'')
##      specification.
## 
## LLEEGGAACCYY DDEESSCCRRIIPPTTIIOONN
##      In legacy mode, the --ff option does not turn on the --aa option and the --gg,
##      --nn, and --oo options do not turn on the --ll option.
## 
##      Also, the --oo option causes the file flags to be included in a long (-l)
##      output; there is no --OO option.
## 
##      When --HH is specified (and not overridden by --LL or --PP) and a file argument
##      is a symlink that resolves to a non-directory file, the output will
##      reflect the nature of the link, rather than that of the file.  In legacy
##      operation, the output will describe the file.
## 
##      For more information about legacy mode, see compat(5).
## 
## SSEEEE AALLSSOO
##      chflags(1), chmod(1), sort(1), xterm(1), compat(5), termcap(5),
##      symlink(7), sticky(8)
## 
## SSTTAANNDDAARRDDSS
##      The llss utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').
## 
## HHIISSTTOORRYY
##      An llss command appeared in Version 1 AT&T UNIX.
## 
## BBUUGGSS
##      To maintain backward compatibility, the relationships between the many
##      options are quite complex.
## 
## BSD                              May 19, 2002                              BSD
```

---

# Help: man (cont.)

A useful feature of `man` is quick pattern searching with "/pattern".
- Try this now by running `$man ls`  again and then typing "/time" and hitting the return key. 
- To continue on to the next case, hit `n`.

</br>

Again, this and other `man` tricks are detailed in the help pages (hit "h").

---

# Help: cheat

I also like the [cheat](https://github.com/cheat/cheat) utility, which provides a more readable summary / cheatsheet of various command. You'll need to install it first. (Linux and MacOS only.)

```
$ cheat ls
## # Displays everything in the target directory
## ls path/to/the/target/directory
## 
## # Displays everything including hidden files
## ls -a
## 
## # Displays all files, along with the size (with unit suffixes) and timestamp
## ls -lh 
## 
## # Display files, sorted by size
## ls -S
## 
## # Display directories only
## ls -d */
## 
## # Display directories only, include hidden
## ls -d .*/ */
```

---
class: inverse, center, middle
name: remote

# Connect to a remote machine

---
# SSH (Secure shell)

### Definition
Cryptographic network protocol for operating network services securely over an unsecured network

You will be using it to connect to computing resources (e.g., `mshresearch`), let's try:
```
# Note that you need to be on a USC network or USC VPN
ssh username@mshreserch.marshall.usc.edu
```
Once you are logged in, you are in your home, check it with `pwd`

You should not save research projects in your home, instead use:
1. `/data/research/  (868G available)
2. `/data-2/research/ (6.9TB available)

As you don't have superuser permission (more on this later), you need to tell me to create a project dir for you

---
class: inverse, center, middle
name: files

# Files and directories

---

# Navigation

Key navigation commands:

- `pwd` to print (the current) working directory.

```bash
pwd
```

```
## /Users/dproserp/phd/teaching/mkt-615/lectures/03-shell
```

---

# Navigation (cont.)

- `cd` to change directory.

You can use absolute paths, but it's better to use relative paths and invoke special symbols for a user's home folder (`~`), current directory (`.`), and parent directory (`..`) as needed.

```bash
pwd
cd examples ## Move into the "examples" sub-directory of this lecture directory.
pwd
cd .. ## Now go back up one directories.
pwd
cd ../.. ## Now go back up two directories.
pwd
```

```
## /Users/dproserp/phd/teaching/mkt-615/lectures/03-shell
## /Users/dproserp/phd/teaching/mkt-615/lectures/03-shell/examples
## /Users/dproserp/phd/teaching/mkt-615/lectures/03-shell
## /Users/dproserp/phd/teaching/mkt-615
```
---

# Navigation (cont.)

Beware of directory names that contain spaces. Say you have a directory called "My Documents". (I'm looking at you, Windows.)

- Why won't `$ cd My Documents` work?

**Answer:** Bash syntax is super pedantic about spaces and ordering. Here it thinks that "My" and "Documents" are separate arguments.

--
Solutions:
  - Use quotation marks: `$ cd "My Documents"`.

- Use Tab completion to automatically "escape" the space: `$ cd My\ Documents`. 
  
  - **BEST PRACTICE: Don't use spaces in file and folder names!**

---

# Listing files and their properties

We're about to go into more depth about the `ls` command.
- To do this effectively, it will be helpful if we're all working off the same group of files and folders.
- Navigate to the directory containing these lecture notes (i.e. `03-shell`). Now list the contents of the  `examples/` sub-directory with the `-lh` option ("long format", "human readable").

```bash
# cd PathWhereYouClonedThisRepo/lectures/03-shell ## change as needed
ls -lh examples
```

```
## total 288
## drwxr-xr-x@ 3 dproserp  staff    96B Nov 13 15:22 ABC
## drwxr-xr-x  3 dproserp  staff    96B Nov 13 15:22 copies
## -rwxrwxr-x@ 1 dproserp  staff   154B Aug 29 14:37 hello.R
## -rwxr-xr-x@ 1 dproserp  staff    30B Aug 24 17:53 hello.sh
## -rwxr-xr-x  1 dproserp  staff    73B Sep 24 07:33 loop.sh
## drwxr-xr-x@ 9 dproserp  staff   288B Aug  2 09:45 meals
## -rw-r--r--@ 1 dproserp  staff    32B Aug  2 09:45 nursery.txt
## -rw-r--r--  1 dproserp  staff   1.8K Aug 11 10:51 output.txt
## -rwxr-xr-x@ 1 dproserp  staff   153B Aug  2 09:45 reps.txt
## -rw-r--r--@ 1 dproserp  staff   117K Aug  2 09:45 sonnets.txt
```

---