Enhance your shell skills

[Daniel-Boll]

Enhance your shell skills

Hello fellow colleagues, we will be using this discussion thread to public some problems in order to anyone try to solve and improve your ability with bash scripting and general usage.

Examples

The following replies will show how we thought as a good way to comprehend this exercises.

How to

Get a problem that you had interest and try to solve it, even though others have already tried to solve it, we will see that you have many many ways to accomplish the same thing and that's what is cool.

1. Find a problem
2. Go to your local pc and try to solve it
3. Document the final solution
4. (optional) Document the process if you think for that process is interesting

Make sure to use markdown features to make your answer prettier. Basic usage will be using: ``` bash in a line, enter all your code bellow and end closing ```

Links

1. Learn the shell
2. (Codecademy) learn the command line
3. Learn bash
4. Learn markdown

---

Good luck and go hack 🤓 💻

Best regards,
Daniel Boll. 🎴

[Daniel-Boll]

Having 3 zipped files as follows:

.rw-r--r-- 152 lambdagroup 16 Jun 00:00 a.zip
.rw-r--r-- 152 lambdagroup 16 Jun 00:00 b.zip
.rw-r--r-- 152 lambdagroup 16 Jun 00:00 c.zip

Extract them all.

[Daniel-Boll]

unzip a.zip
unzip b.zip
unzip c.zip

[Daniel-Boll]

find . -name '*.zip' -exec unzip {} \;

Using the find command I manage to get it in only one command 😄

[Daniel-Boll]

Curl your location weather with https://wttr.in/.

[Daniel-Boll]

curl wttr.in

Gave me an awesome output

[Daniel-Boll]

http wttr.in

Dependencies

• httpie

[Daniel-Boll]

wget -qO- wttr.in | more

Dependencies

I think that the more command is available with less

Explanation

I used the wget command with the flags:

• -q (which disable the output of downloading status and all that gibberish.
• -O- (the O flag output to a file, but I'm saying to - to the standard output. It can also be written as wget -q -O -)

Then I piped to more because it supports the special outputs required to display colors and all.

[Daniel-Boll]

Following the example of @Daniel-Boll I tried to use httpie and also extracted that to a bash script so I could use it as:

weather_at -c 'toledo'

Of course, once I give it the right privileges and add it to a folder under $PATH

#!/usr/bin/env bash

CITY=""

usage() {
    echo "Usage: $0 -c <city> [-h]"
    echo "  -c <city>  City to get weather for"
    echo "  -h         Show this help"
}

check_depencies() {
  # Use command -v to check if the command is installed
  if ! command -v http >/dev/null 2>&1; then
    echo "http is not installed"
    exit 1
  fi
}

check_depencies

# Get the city name from the flag c
while getopts "c:h" opt; do
  case $opt in
    c)
      CITY=$OPTARG
      if [ -z "$CITY" ]; then
        echo "Error: City name is required"
        exit 1
      fi
      ;;
    h)
      usage
      exit 0
      ;;
    \?)
      echo "Invalid option: -$OPTARG" >&2
      usage
      exit 1
      ;;
    :)
      echo "Option -$OPTARG requires an argument." >&2
      usage
      exit 1
      ;;
  esac
done

http wttr.in/"${CITY}"

Dependencies

• httpie

Explanation

I used getopts to get the option from the user and command to check if a command is installed. I suggest yall check those because they will be very convenient for scripts.

How to run

1. Add the script to a file named weather_at
2. Run it with bash weather_at -c 'cascavel'
3. (optional) Give it execution privileges with chmod +x ./weather_at and add it to a $PATH folder in order to access it anywhere.

[Mulling]

wget -qO- wttr.in | more

Dependencies

I think that the more command is available with less

Explanation

I used the wget command with the flags:

• -q (which disable the output of downloading status and all that gibberish.
• -O- (the O flag output to a file, but I'm saying to - to the standard output. It can also be written as wget -q -O -)

Then I piped to more because it supports the special outputs required to display colors and all.

To use less instead of more you need to pass the -R flag to force the raw vt100 escape codes to be rendered as colors.

wget -qO- wttr.in | less -R

[Daniel-Boll]

Having the files:

.rw-r--r-- 0 lambdagroup 16 Jun 00:00 a.png
.rw-r--r-- 0 lambdagroup 16 Jun 00:00 b.pdf
.rw-r--r-- 0 lambdagroup 16 Jun 00:00 c.webp
.rw-r--r-- 0 lambdagroup 16 Jun 00:00 d.txt
.rw-r--r-- 0 lambdagroup 16 Jun 00:00 e.txt
.rw-r--r-- 0 lambdagroup 16 Jun 00:00 f.txt

Count how many .txt files there is.

[Mulling]

Tip: to create the files you can use:

touch {a.png,b.pdf,c.webp,d.txt,e.txt,f.txt}

[Daniel-Boll]

You can also separate the values like

touch a b c

or like Mulling suggested using the expansion which is super powerful, where you can do things like:

touch {{a,b,c}.txt,{d,e}.{pdf,png}}

Which produces the files
a.txt b.txt c.txt d.pdf d.png e.pdf e.png

[Mulling]

Follow the steps below using the command line:

1. Create a directory named dir
2. Navigate to dir
3. Crate a file named file
4. Write "Hello World" into the file (tip: steps 3 and 4 can be done in a single command)
5. Display the contents of the file
6. Edit the contents of the file to contain the phrase "Hello Cruel World" without opening it in a text editor (tip: use sed -i)
7. Display the contents of the file (again)
8. Navigate back to the previous directory
9. Remove the directory dir and the file file (tip: use rm -ri)

[Daniel-Boll]

Print which shell you are in.

[Mulling]

Also, while you are at it, print the path of the home directory of your current user.

[Daniel-Boll]

Requirement

It must be a one-liner, no file scripts nor ; (except in cases like for's and if's) allowed.

---

Print the message Yes, it is if the current user is within the group wheel otherwise print the message No, it's not.

Tips: /dev/null && ||

[Mulling]

People,

This page has a few bash exercises, i suggest doing the first ones.