Tcl 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. Tcl

load ./chilkat.dll

set success 0

set success 0

#  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.
set sbCurl [new_CkStringBuilder]

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 "}\""

set curl [new_CkHttpCurl]

#  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.
set sbRawRequest [new_CkStringBuilder]

set success [CkHttpCurl_ToRawRequest $curl [CkStringBuilder_getAsString $sbCurl] $sbRawRequest]
if {$success == 0} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkStringBuilder $sbCurl
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $sbRawRequest
    exit
}

puts [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
#    }
#  }

delete_CkStringBuilder $sbCurl
delete_CkHttpCurl $curl
delete_CkStringBuilder $sbRawRequest