B4X Requires Chilkat v11.7.0+
Box: Find a File by Name Across All Folder Pages

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. Find one exact, case-sensitive filename in a parent folder selected by name, checking the item type and every page before using its ID.
See the Box API guide for setup and the complete workflow.
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Dim success As Boolean = False

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

success = False

'  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.
Dim curl As ChilkatHttpCurl
curl.Initialize("curl")
curl.SetVar("access_token", "BOX_ACCESS_TOKEN")
curl.SetVar("parent_name", "/")
'  Box's fixed root ID is an implementation detail; callers supply names.
curl.SetVar("parent_id", "0")
Dim setupCommand As ChilkatStringBuilder
setupCommand.Initialize
Dim setupReplacements As Int

'  Register findParent; registration sends no request.
setupCommand.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer ACCESS_TOKEN" & Chr(34))
setupReplacements = setupCommand.Replace("ACCESS_TOKEN", curl.GetVar("access_token"))
success = curl.AddFunction("findParent", setupCommand.GetAsString)
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If


'  Register findFolder; registration sends no request.
setupCommand.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/folders/{{parent_id}}/items?limit=1000&fields=id,type,name" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer ACCESS_TOKEN" & Chr(34))
setupReplacements = setupCommand.Replace("ACCESS_TOKEN", curl.GetVar("access_token"))
success = curl.AddFunction("findFolder", setupCommand.GetAsString)
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If


'  Register findFile; registration sends no request.
setupCommand.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/folders/{{folder_id}}/items?limit=1000&fields=id,type,name" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer ACCESS_TOKEN" & Chr(34))
setupReplacements = setupCommand.Replace("ACCESS_TOKEN", curl.GetVar("access_token"))
success = curl.AddFunction("findFile", setupCommand.GetAsString)
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If


'  Register findDestination; registration sends no request.
setupCommand.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer ACCESS_TOKEN" & Chr(34))
setupReplacements = setupCommand.Replace("ACCESS_TOKEN", curl.GetVar("access_token"))
success = curl.AddFunction("findDestination", setupCommand.GetAsString)
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If


'  Register getFileDetails; registration sends no request.
setupCommand.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/files/{{file_id}}?fields=id,sha1,file_version" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer ACCESS_TOKEN" & Chr(34))
setupReplacements = setupCommand.Replace("ACCESS_TOKEN", curl.GetVar("access_token"))
success = curl.AddFunction("getFileDetails", setupCommand.GetAsString)
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If


'  Register getEnterprise; registration sends no request.
setupCommand.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/users/me?fields=enterprise" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer ACCESS_TOKEN" & Chr(34))
setupReplacements = setupCommand.Replace("ACCESS_TOKEN", curl.GetVar("access_token"))
success = curl.AddFunction("getEnterprise", setupCommand.GetAsString)
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If


'  Register output rules once. Chilkat 11.7.0 evaluates {{name}} variables
'  when extracting each output, using the current value at that time.
success = curl.AddOutput2("findParent", "entries", "name", "{{parent_name}}", True, "id", "parent_id")
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If

success = curl.AddOutput2("findFolder", "entries", "name", "{{folder_name}}", True, "id", "folder_id")
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If

success = curl.AddOutput2("findFile", "entries", "name", "{{file_name}}", True, "id", "file_id")
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If

success = curl.AddOutput2("findDestination", "entries", "name", "{{destination_name}}", True, "id", "destination_id")
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If

success = curl.AddOutput("getFileDetails", "file_version.id", "file_version_id")
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If

success = curl.AddOutput("getFileDetails", "sha1", "file_sha1")
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If

success = curl.AddOutput("getEnterprise", "enterprise.id", "enterprise_id")
If success <> True Then
    Log(curl.LastErrorText)
    Return
End If

'  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.
Dim parentName As String = "/"
Dim folderName As String = "images"
If (curl.GetVar("parent_name") <> parentName) Or ((parentName = "/") And (curl.VarDefined("parent_id") = False)) Then
    curl.SetVar("parent_name", parentName)
    curl.ClearVar("parent_id")
    curl.ClearVar("folder_id")
    curl.ClearVar("file_id")
    curl.ClearVar("file_version_id")
    curl.ClearVar("file_sha1")
    If parentName = "/" Then
        curl.SetVar("parent_id", "0")
    End If

End If

If curl.GetVar("folder_name") <> folderName Then
    curl.SetVar("folder_name", folderName)
    curl.ClearVar("folder_id")
    curl.ClearVar("file_id")
    curl.ClearVar("file_version_id")
    curl.ClearVar("file_sha1")
End If

curl.SetVar("marker", "")
Dim page As ChilkatJsonObject
page.Initialize
Dim i As Int = 0
Dim count As Int = 0
Dim more As Boolean = True
Dim nextMarker As String
Dim authorizedCommand1 As ChilkatStringBuilder
authorizedCommand1.Initialize
authorizedCommand1.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/folders/{{folder_id}}/items?usemarker=true&limit=1000&fields=id,type,name" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer {{access_token}}" & Chr(34))
Dim headerReplacement1 As Int = authorizedCommand1.Replace("{{access_token}}", curl.GetVar("access_token"))
Dim pageCommand As String = authorizedCommand1.GetAsString
Dim wantedName As String = "penguins.jpg"
Dim fileId As String = ""
Dim matches As Int = 0
Do While (more = True)
    curl.ClearTargetOutput("*")
    success = curl.DoYourThing(pageCommand)
    If (success <> True) Or (curl.StatusCode <> 200) Then
        Log("Box request failed. HTTP status: " & curl.StatusCode)
        Log("Failure reason: " & curl.FailReason)
        Log(curl.ResponseBodyStr)
        Return
    End If

    success = curl.GetResponseJson(page)
    If success <> True Then
        Log(curl.LastErrorText)
        Return
    End If

    count = page.SizeOfArray("entries")
    i = 0
    Do While i < count
        page.I = i
        If (page.StringOf("entries[i].type") = "file") And (page.StringOf("entries[i].name") = wantedName) Then
            fileId = page.StringOf("entries[i].id")
            matches = matches + 1
        End If

        i = i + 1
    Loop
    more = False
    If page.HasMember("next_marker") = True Then
        If page.IsNullOf("next_marker") = False Then
            nextMarker = page.StringOf("next_marker")
            If nextMarker <> "" Then
                If nextMarker = curl.GetVar("marker") Then
                    Log("Box returned the same pagination marker; stopping.")
                    Return
                End If

                curl.SetVar("marker", nextMarker)
                Dim authorizedCommand2 As ChilkatStringBuilder
                authorizedCommand2.Initialize
                authorizedCommand2.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/folders/{{folder_id}}/items?usemarker=true&limit=1000&fields=id,type,name&marker={{marker}}" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer {{access_token}}" & Chr(34))
                Dim headerReplacement2 As Int = authorizedCommand2.Replace("{{access_token}}", curl.GetVar("access_token"))
                pageCommand = authorizedCommand2.GetAsString
                more = True
            End If

        End If

    End If

Loop
If matches <> 1 Then
    Log("Expected exactly one matching file. Matches: " & matches)
    Return
End If

curl.SetVar("file_id", fileId)
Log("File ID: " & fileId)
curl.ClearTargetOutput("*")
Dim authorizedCommand3 As ChilkatStringBuilder
authorizedCommand3.Initialize
authorizedCommand3.SetString("curl -X GET " & Chr(34) & "https://api.box.com/2.0/files/{{file_id}}?fields=id,type,name,parent,size" & Chr(34) & " -H " & Chr(34) & "Authorization: Bearer {{access_token}}" & Chr(34))
Dim headerReplacement3 As Int = authorizedCommand3.Replace("{{access_token}}", curl.GetVar("access_token"))
success = curl.DoYourThing(authorizedCommand3.GetAsString)
If (success <> True) Or (curl.StatusCode <> 200) Then
    Log("Box request failed. HTTP status: " & curl.StatusCode)
    Log("Failure reason: " & curl.FailReason)
    Log(curl.ResponseBodyStr)
    Return
End If

Log(curl.ResponseBodyStr)