Zig Requires Chilkat v11.5.0+

curl with Variable Substitution in a GraphQL Request Body

See more CURL Examples

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

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    var success: bool = false;

    success = false;

    // Variable names are enclosed between {{ and }}
    // Important: Variables should be placed inside the quotes.

    // curl -X POST https://api.example.com/graphql \
    //   -H "Content-Type: application/graphql; charset=utf-8" \
    //   -H "Accept: application/json" \
    //   --data-binary "mutation {
    //   createUser(
    //     input: {
    //       name: \"{{name}}\"
    //       city: \"{{city}}\"
    //       note: \"{{note}}\"
    //       bio: \"{{bio}}\"
    //     }
    //   ) {
    //     id
    //     name
    //   }
    // }"

    // Build the above curl command.
    const sb_curl = try chilkat.StringBuilder.init();
    defer sb_curl.deinit();
    sb_curl.appendLn("curl -X POST https://api.example.com/graphql \\") catch {};
    sb_curl.appendLn("  -H \"Content-Type: application/graphql; charset=utf-8\" \\") catch {};
    sb_curl.appendLn("  -H \"Accept: application/json\" \\") catch {};
    sb_curl.appendLn("  -d \"mutation {") catch {};
    sb_curl.appendLn("  createUser(") catch {};
    sb_curl.appendLn("    input: {") catch {};
    sb_curl.appendLn("      name: \\\"{{name}}\\\"") catch {};
    sb_curl.appendLn("      city: \\\"{{city}}\\\"") catch {};
    sb_curl.appendLn("      note: \\\"{{note}}\\\"") catch {};
    sb_curl.appendLn("      bio: \\\"{{bio}}\\\"") catch {};
    sb_curl.appendLn("    }") catch {};
    sb_curl.appendLn("  ) {") catch {};
    sb_curl.appendLn("    id") catch {};
    sb_curl.appendLn("    name") catch {};
    sb_curl.appendLn("  }") catch {};
    sb_curl.appendLn("}\"") catch {};

    const curl = try chilkat.HttpCurl.init();
    defer curl.deinit();

    // Provide values for variables
    curl.setVar("name", "José O'Connor");
    curl.setVar("city", "München");
    curl.setVar("note", "He said \"Hello, world!\" — and left…");
    curl.setVar("bio", "Loves sushi, café visits, and π ≈ 3.14159");

    // 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.
    const sb_raw_request = try chilkat.StringBuilder.init();
    defer sb_raw_request.deinit();
    curl.toRawRequest(try sb_curl.getAsString(alloc), sb_raw_request) catch {
        std.debug.print("{s}\n", .{try curl.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("{s}\n", .{try sb_raw_request.getAsString(alloc)});

    // The output is shown below.
    // Notice the quote chars around "Hello, world!" are properly escaped.

    // POST /graphql HTTP/1.1
    // Accept: application/json
    // Host: api.example.com
    // Content-Type: application/graphql; charset=utf-8
    // Content-Length: 250
    //
    // mutation {
    //   createUser(
    //     input: {
    //       name: "José O'Connor"
    //       city: "München"
    //       note: "He said \"Hello, world!\" — and left…"
    //       bio: "Loves sushi, café visits, and π ≈ 3.14159"
    //     }
    //   ) {
    //     id
    //     name
    //   }
    // }
}