Perl

curl with Variable Substitution in a JSON Request Body

See more CURL Examples

This example shows how to use variables inside a JSON request body using the {{variable_name}} syntax. When the HTTP request’s Content-Type indicates JSON, Chilkat automatically applies proper JSON escaping to each substituted value, ensuring the resulting JSON remains valid. Perl

use chilkat();

$success = 0;

# Variable names are enclosed between {{ and }}
# Important: The variable {{var_name}} should be placed inside the quotes.

# This is correct:
# curl -X POST https://api.example.com/messages \
#   -H "Content-Type: application/json" \
#   -d '{"text":"{{message}}"}'

# This is incorrect:
#   -d '{"text":{{message}}}'

$sbCurl = chilkat::CkStringBuilder->new();
$sbCurl->AppendLn("curl -X POST https://api.example.com/messages \\");
$sbCurl->AppendLn("  -H \"Content-Type: application/json\" \\");
$sbCurl->AppendLn("  -d '{\"text\":\"{{message}}\"}'");

$curl = chilkat::CkHttpCurl->new();

# In this example, the value we'll provide for the "message" variable
# will contain chars that require JSON escaping.
$curl->SetVar("message","He said \"Hello, world!\"");

# To demonstrate how the variables are replaced, this example does not execute the curl command. 
# Instead, it generates the raw HTTP request that would be sent if the curl command were run.
$sbRawRequest = chilkat::CkStringBuilder->new();
$success = $curl->ToRawRequest($sbCurl->getAsString(),$sbRawRequest);
if ($success == 0) {
    print $curl->lastErrorText() . "\r\n";
    exit;
}

print $sbRawRequest->getAsString() . "\r\n";

# The output is shown below.
# Notice that the quote chars around "Hello World!" are properly JSON escaped.

# POST /messages HTTP/1.1
# Host: api.example.com
# Content-Type: application/json
# Content-Length: 36
# 
# {"text":"He said \"Hello, world!\""}