Tcl Requires Chilkat v11.7.0+
Box: Reuse HttpCurl and Invalidate Cached IDs

Run the reusable setup once per HttpCurl object, then select names and execute the operation. The setup is repeated here only to make this published example independently runnable. Perform three operations with one configured object: cold file lookup, warm download without lookups, then another download to a different local path after clearing only file state. Functions and output rules are registered only once; their variables are evaluated when used.
See the Box API guide for setup and the complete workflow.
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Tcl

load ./chilkat.dll

set success 0

#  Requires Chilkat 11.7.0 or later and a previously unlocked Chilkat bundle.
#  See Global Unlock Sample.
#  Guide: Box API Guide.

set success 0

#  BEGIN ONE-TIME SETUP
#  This block is repeated so each published example can run on its own.
#  In an application, run the setup example once and pass the SAME curl object
#  to operation code below. Do not recreate it for every operation.
#  See Reusable Box HttpCurl Setup.
set curl [new_CkHttpCurl]

CkHttpCurl_SetVar $curl "access_token" "BOX_ACCESS_TOKEN"
CkHttpCurl_SetVar $curl "parent_name" "/"
#  Box's fixed root ID is an implementation detail; callers supply names.
CkHttpCurl_SetVar $curl "parent_id" "0"
set setupCommand [new_CkStringBuilder]

#  Register findParent; registration sends no request.
CkStringBuilder_SetString $setupCommand "curl -X GET \"https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name\" -H \"Authorization: Bearer ACCESS_TOKEN\""
set setupReplacements [CkStringBuilder_Replace $setupCommand "ACCESS_TOKEN" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_AddFunction $curl "findParent" [CkStringBuilder_getAsString $setupCommand]]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

#  Register findFolder; registration sends no request.
CkStringBuilder_SetString $setupCommand "curl -X GET \"https://api.box.com/2.0/folders/{{parent_id}}/items?limit=1000&fields=id,type,name\" -H \"Authorization: Bearer ACCESS_TOKEN\""
set setupReplacements [CkStringBuilder_Replace $setupCommand "ACCESS_TOKEN" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_AddFunction $curl "findFolder" [CkStringBuilder_getAsString $setupCommand]]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

#  Register findFile; registration sends no request.
CkStringBuilder_SetString $setupCommand "curl -X GET \"https://api.box.com/2.0/folders/{{folder_id}}/items?limit=1000&fields=id,type,name\" -H \"Authorization: Bearer ACCESS_TOKEN\""
set setupReplacements [CkStringBuilder_Replace $setupCommand "ACCESS_TOKEN" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_AddFunction $curl "findFile" [CkStringBuilder_getAsString $setupCommand]]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

#  Register findDestination; registration sends no request.
CkStringBuilder_SetString $setupCommand "curl -X GET \"https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name\" -H \"Authorization: Bearer ACCESS_TOKEN\""
set setupReplacements [CkStringBuilder_Replace $setupCommand "ACCESS_TOKEN" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_AddFunction $curl "findDestination" [CkStringBuilder_getAsString $setupCommand]]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

#  Register getFileDetails; registration sends no request.
CkStringBuilder_SetString $setupCommand "curl -X GET \"https://api.box.com/2.0/files/{{file_id}}?fields=id,sha1,file_version\" -H \"Authorization: Bearer ACCESS_TOKEN\""
set setupReplacements [CkStringBuilder_Replace $setupCommand "ACCESS_TOKEN" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_AddFunction $curl "getFileDetails" [CkStringBuilder_getAsString $setupCommand]]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

#  Register getEnterprise; registration sends no request.
CkStringBuilder_SetString $setupCommand "curl -X GET \"https://api.box.com/2.0/users/me?fields=enterprise\" -H \"Authorization: Bearer ACCESS_TOKEN\""
set setupReplacements [CkStringBuilder_Replace $setupCommand "ACCESS_TOKEN" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_AddFunction $curl "getEnterprise" [CkStringBuilder_getAsString $setupCommand]]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

#  Register output rules once. Chilkat 11.7.0 evaluates {{name}} variables
#  when extracting each output, using the current value at that time.
set success [CkHttpCurl_AddOutput2 $curl "findParent" "entries" "name" "{{parent_name}}" 1 "id" "parent_id"]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

set success [CkHttpCurl_AddOutput2 $curl "findFolder" "entries" "name" "{{folder_name}}" 1 "id" "folder_id"]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

set success [CkHttpCurl_AddOutput2 $curl "findFile" "entries" "name" "{{file_name}}" 1 "id" "file_id"]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

set success [CkHttpCurl_AddOutput2 $curl "findDestination" "entries" "name" "{{destination_name}}" 1 "id" "destination_id"]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

set success [CkHttpCurl_AddOutput $curl "getFileDetails" "file_version.id" "file_version_id"]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

set success [CkHttpCurl_AddOutput $curl "getFileDetails" "sha1" "file_sha1"]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

set success [CkHttpCurl_AddOutput $curl "getEnterprise" "enterprise.id" "enterprise_id"]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    exit
}

#  END ONE-TIME SETUP
#  The name lookups below assume each listing fits in one page (1000 items).
#  Parent and destination names select root children; folder_name selects a child
#  of parent_name. "/" selects the root parent. These are not arbitrary paths.

#  BEGIN OPERATION -- keep the configured object when reusing it.
#  Inputs are names. Retain cached IDs when the selected names have not changed.
set parentName "/"
set folderName "images"
set fileName "penguins.jpg"
if {expr [[CkHttpCurl_getVar $curl "parent_name"] != $parentName]  ||  [expr [$parentName == "/"]  &&  [[CkHttpCurl_VarDefined $curl "parent_id"] == 0]]} then {
    CkHttpCurl_SetVar $curl "parent_name" $parentName
    CkHttpCurl_ClearVar $curl "parent_id"
    CkHttpCurl_ClearVar $curl "folder_id"
    CkHttpCurl_ClearVar $curl "file_id"
    CkHttpCurl_ClearVar $curl "file_version_id"
    CkHttpCurl_ClearVar $curl "file_sha1"
    if {$parentName == "/"} then {
        CkHttpCurl_SetVar $curl "parent_id" "0"
    }

}

if {[CkHttpCurl_getVar $curl "folder_name"] != $folderName} then {
    CkHttpCurl_SetVar $curl "folder_name" $folderName
    CkHttpCurl_ClearVar $curl "folder_id"
    CkHttpCurl_ClearVar $curl "file_id"
    CkHttpCurl_ClearVar $curl "file_version_id"
    CkHttpCurl_ClearVar $curl "file_sha1"
}

if {[CkHttpCurl_getVar $curl "file_name"] != $fileName} then {
    CkHttpCurl_SetVar $curl "file_name" $fileName
    CkHttpCurl_ClearVar $curl "file_id"
    CkHttpCurl_ClearVar $curl "file_version_id"
    CkHttpCurl_ClearVar $curl "file_sha1"
}

CkHttpCurl_SetVar $curl "local_path" "qa_output/penguins.jpg"
#  Operation 1: get information by name. This resolves folder_id and file_id.
CkHttpCurl_ClearTargetOutput $curl "*"
set authorizedCommand1 [new_CkStringBuilder]

CkStringBuilder_SetString $authorizedCommand1 "curl -X GET \"https://api.box.com/2.0/files/{{file_id}}?fields=id,name\" -H \"Authorization: Bearer {{access_token}}\""
set headerReplacement1 [CkStringBuilder_Replace $authorizedCommand1 "{{access_token}}" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_DoYourThing $curl [CkStringBuilder_getAsString $authorizedCommand1]]
if {expr [$success != 1]  ||  [[CkHttpCurl_get_StatusCode $curl] != 200]} then {
    puts "Box request failed. HTTP status: [CkHttpCurl_get_StatusCode $curl]"
    puts "Failure reason: [CkHttpCurl_get_FailReason $curl]"
    puts [CkHttpCurl_responseBodyStr $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    delete_CkStringBuilder $authorizedCommand1
    exit
}

#  Operation 2: keep the same object and IDs. Only the final download is needed.
set warmPlan [new_CkJsonObject]

CkJsonObject_put_EmitCompact $warmPlan 0
set authorizedCommand2 [new_CkStringBuilder]

CkStringBuilder_SetString $authorizedCommand2 "curl -X GET \"https://api.box.com/2.0/files/{{file_id}}/content\" -H \"Authorization: Bearer {{access_token}}\" -L -o \"{{local_path}}\""
set headerReplacement2 [CkStringBuilder_Replace $authorizedCommand2 "{{access_token}}" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_ExaminePlan $curl [CkStringBuilder_getAsString $authorizedCommand2] $warmPlan]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    delete_CkStringBuilder $authorizedCommand1
    delete_CkJsonObject $warmPlan
    delete_CkStringBuilder $authorizedCommand2
    exit
}

puts [CkJsonObject_emit $warmPlan]
CkHttpCurl_ClearTargetOutput $curl "*"
set authorizedCommand3 [new_CkStringBuilder]

CkStringBuilder_SetString $authorizedCommand3 "curl -X GET \"https://api.box.com/2.0/files/{{file_id}}/content\" -H \"Authorization: Bearer {{access_token}}\" -L -o \"{{local_path}}\""
set headerReplacement3 [CkStringBuilder_Replace $authorizedCommand3 "{{access_token}}" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_DoYourThing $curl [CkStringBuilder_getAsString $authorizedCommand3]]
if {expr [$success != 1]  ||  [[CkHttpCurl_get_StatusCode $curl] != 200]} then {
    puts "Box request failed. HTTP status: [CkHttpCurl_get_StatusCode $curl]"
    puts "Failure reason: [CkHttpCurl_get_FailReason $curl]"
    puts [CkHttpCurl_responseBodyStr $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    delete_CkStringBuilder $authorizedCommand1
    delete_CkJsonObject $warmPlan
    delete_CkStringBuilder $authorizedCommand2
    delete_CkStringBuilder $authorizedCommand3
    exit
}

#  Operation 3: explicitly invalidate file state, retaining the known folder.
#  Here we select the same name so this demonstration needs only one real file.
#  Substitute another filename to switch files in this folder.
#  The existing output rule reads the current file_name; do not register it again.
CkHttpCurl_ClearVar $curl "file_id"
CkHttpCurl_ClearVar $curl "file_version_id"
CkHttpCurl_ClearVar $curl "file_sha1"
CkHttpCurl_SetVar $curl "file_name" "penguins.jpg"
CkHttpCurl_SetVar $curl "local_path" "qa_output/penguins-copy.jpg"
set authorizedCommand4 [new_CkStringBuilder]

CkStringBuilder_SetString $authorizedCommand4 "curl -X GET \"https://api.box.com/2.0/files/{{file_id}}/content\" -H \"Authorization: Bearer {{access_token}}\" -L -o \"{{local_path}}\""
set headerReplacement4 [CkStringBuilder_Replace $authorizedCommand4 "{{access_token}}" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_ExaminePlan $curl [CkStringBuilder_getAsString $authorizedCommand4] $warmPlan]
if {$success != 1} then {
    puts [CkHttpCurl_lastErrorText $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    delete_CkStringBuilder $authorizedCommand1
    delete_CkJsonObject $warmPlan
    delete_CkStringBuilder $authorizedCommand2
    delete_CkStringBuilder $authorizedCommand3
    delete_CkStringBuilder $authorizedCommand4
    exit
}

puts [CkJsonObject_emit $warmPlan]
CkHttpCurl_ClearTargetOutput $curl "*"
set authorizedCommand5 [new_CkStringBuilder]

CkStringBuilder_SetString $authorizedCommand5 "curl -X GET \"https://api.box.com/2.0/files/{{file_id}}/content\" -H \"Authorization: Bearer {{access_token}}\" -L -o \"{{local_path}}\""
set headerReplacement5 [CkStringBuilder_Replace $authorizedCommand5 "{{access_token}}" [CkHttpCurl_getVar $curl "access_token"]]
set success [CkHttpCurl_DoYourThing $curl [CkStringBuilder_getAsString $authorizedCommand5]]
if {expr [$success != 1]  ||  [[CkHttpCurl_get_StatusCode $curl] != 200]} then {
    puts "Box request failed. HTTP status: [CkHttpCurl_get_StatusCode $curl]"
    puts "Failure reason: [CkHttpCurl_get_FailReason $curl]"
    puts [CkHttpCurl_responseBodyStr $curl]
    delete_CkHttpCurl $curl
    delete_CkStringBuilder $setupCommand
    delete_CkStringBuilder $authorizedCommand1
    delete_CkJsonObject $warmPlan
    delete_CkStringBuilder $authorizedCommand2
    delete_CkStringBuilder $authorizedCommand3
    delete_CkStringBuilder $authorizedCommand4
    delete_CkStringBuilder $authorizedCommand5
    exit
}

#  Changing parent_name invalidates parent_id, folder_id, and file state.
#  Changing folder_name invalidates folder_id and file state.
#  Changing destination_name invalidates destination_id.

delete_CkHttpCurl $curl
delete_CkStringBuilder $setupCommand
delete_CkStringBuilder $authorizedCommand1
delete_CkJsonObject $warmPlan
delete_CkStringBuilder $authorizedCommand2
delete_CkStringBuilder $authorizedCommand3
delete_CkStringBuilder $authorizedCommand4
delete_CkStringBuilder $authorizedCommand5