C

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. C

#include <C_CkStringBuilder.h>
#include <C_CkHttpCurl.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkStringBuilder sbCurl;
    HCkHttpCurl curl;
    HCkStringBuilder sbRawRequest;

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

    curl = CkHttpCurl_Create();

    // Provide values for variables
    CkHttpCurl_SetVar(curl,"name","José O'Connor");
    CkHttpCurl_SetVar(curl,"city","München");
    CkHttpCurl_SetVar(curl,"note","He said \"Hello, world!\" — and left…");
    CkHttpCurl_SetVar(curl,"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.
    sbRawRequest = CkStringBuilder_Create();
    success = CkHttpCurl_ToRawRequest(curl,CkStringBuilder_getAsString(sbCurl),sbRawRequest);
    if (success == FALSE) {
        printf("%s\n",CkHttpCurl_lastErrorText(curl));
        CkStringBuilder_Dispose(sbCurl);
        CkHttpCurl_Dispose(curl);
        CkStringBuilder_Dispose(sbRawRequest);
        return;
    }

    printf("%s\n",CkStringBuilder_getAsString(sbRawRequest));

    // 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
    //   }
    // }


    CkStringBuilder_Dispose(sbCurl);
    CkHttpCurl_Dispose(curl);
    CkStringBuilder_Dispose(sbRawRequest);

    }