API interaction scripts in Bash Scripting - Step-by-Step Execution

Concept Flow - API interaction scripts

Start script

↓

Prepare API URL & data

↓

Send HTTP request with curl

↓

Receive response

↓

Check response status

↓

Process data

↓

End script

The script prepares the API request, sends it, checks the response, and processes or handles errors accordingly.

Execution Sample

Bash Scripting

url="https://api.agify.io?name=michael"
curl -s "$url" -o response.json
status=$?
if [ $status -eq 0 ]; then
  cat response.json
else
  echo "Request failed"
fi

This script calls an API to guess age by name, saves response, and prints it if successful.

Execution Table

Step	Action	Command/Check	Result/Output
1	Set API URL	url="https://api.agify.io?name=michael"	url variable set
2	Send HTTP GET request	curl -s "$url" -o response.json	response.json file created with API data
3	Check curl exit status	status=$?	status=0 (success)
4	Condition check	if [ $status -eq 0 ]	True branch taken
5	Output response content	cat response.json	{"name":"michael","age":69,"count":12345}
6	End script	fi	Script ends normally

💡 curl command succeeds (exit status 0), so response is printed and script ends

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
url	unset	https://api.agify.io?name=michael	https://api.agify.io?name=michael	https://api.agify.io?name=michael
status	unset	unset	0	0

Key Moments - 2 Insights

Why do we check the variable 'status' after running curl?

Because 'status' holds curl's exit code; 0 means success. This check decides if we print the response or show an error (see execution_table step 3 and 4).

What happens if the API request fails?

If curl fails, 'status' is not 0, so the else branch runs and prints 'Request failed' (not shown in this run but implied by the if-else structure).

Visual Quiz - 3 Questions

Look at the execution table at step 3, what does the variable 'status' equal?

A 1

B 0

C Undefined

D Curl command

💡 Hint

Check the 'Result/Output' column at step 3 in the execution_table.

At which step does the script decide to print the API response?

A Step 4

B Step 5

C Step 2

D Step 6

💡 Hint

Look at the 'Condition check' step where the if statement chooses the branch.

If the curl command failed, what would the script output?

A Nothing

B The API response JSON

C Request failed

D An error code number

💡 Hint

Refer to the if-else logic in the execution_sample code and key_moments about failure handling.

Concept Snapshot

API interaction scripts in bash:
- Set API URL in a variable
- Use curl to send HTTP request
- Check curl exit status ($?)
- If success, process or print response
- Else, handle error (print message)
Simple, stepwise flow for reliable API calls.

Full Transcript

This visual execution shows a bash script that interacts with an API. First, it sets the API URL in a variable. Then it uses curl to send a GET request silently and saves the response to a file. After curl runs, the script checks its exit status stored in 'status'. If status is zero, meaning success, it prints the response content. Otherwise, it prints 'Request failed'. Variables 'url' and 'status' change as the script runs. Key moments include understanding why we check curl's exit status and what happens on failure. The quiz tests understanding of these steps and outcomes.