Example scripts

Example scripts that you can use in your lifecycle scripts.

These example scripts may use software that is not be available on every operating system.

Track setup scripts

Wait for bootstrap

Wait for the Instruqt bootstrap process to complete.

Bash

#!/bin/bash
set -euxo pipefail

until [ -f /opt/instruqt/bootstrap/host-bootstrap-completed ]; do
    echo "Waiting for instruqt bootstrap to complete"    sleep 1
done

The bootstrap process may overwrite user files like .bashrc. Wait is encouraged!

Wait for service

Wait for a specific web service in your setup script to finish booting.

Bash

while ! curl --fail --output /dev/null https://<hostname>:<port>/<path> 
do
    sleep 1
done

Create a file

Create a file using heredoc method.

Bash

cat > /file/to/create <<EOF
# Some configuration file
setting_one = true
another_setting = false
EOF

You can append to a file by using >> as opposed to >.

Download files

Download files to the local system.

Bash (Git)

git clone https://githost.com/repo <local_dir>

Bash (Curl)

curl http://example.com/folder/big-file.iso -O <local_file>

Start background process

Start a process in the background so your script does not hang.

Bash

nohup ./myprogram > foo.out 2> foo.err < /dev/null & disown

Challenge check scripts

File exists

Check if a file exists:

Bash

#!/bin/bash
set -euxo pipefail

if [ -f /home/user/file.txt ]; then
    echo "The file at /home/user/file.txt exists"
fi

File doesn't exist

Check if a file doesn't exist (or is not a file):

Bash

#!/bin/bash
set -euxo pipefail

if [ ! -f /home/user/file.txt ]; then
    fail-message "No file was found at /home/user/file.txt"
fi

Directory exists

Check if a directory exists:

Bash

#!/bin/bash
set -euxo pipefail

if [ -d /root/folder ]; then
    echo "The directory at /root/folder exists"
fi

Directory doesn't exist

Use the following code in your life cycle script to check if a folder doesn't exist (or is not a directory)

Bash

#!/bin/bash
set -euxo pipefail

if [ ! -d /root/folder ]; then
    fail-message "The folder at /root/folder doesn't exists"
fi

File contains certain text

Check if a file contains certain text.

Bash

#!/bin/bash
set -euxo pipefail

if ! grep "text to find" /path/to/file; then
    fail-message "The file doesn't contain the required text"
fi

Specific command is installed

Check that a specific command is executable with the -x flag.

Bash

#!/bin/bash
set -euxo pipefail

if ! [[ -x /usr/local/bin/command ]]; then
  fail-message "Oops, command was not found or is not executable."
fi

Service is running

Check if a service is running.

Bash

#!/bin/bash
if pgrep -x SERVICE >/dev/null; then
    echo "The X service is running"
fi

Replace SERVICE with a service name running on that system.