ftp - Client-side tcl implementation of the ftp protocol
The ftp package provides the client side of the ftp protocol as specified in RFC 959 (http://www.rfc-editor.org/rfc/rfc959.txt). The package implements both active (default) and passive ftp sessions.
A new ftp session is started with the ::ftp::Open command. To shutdown an existing ftp session use ::ftp::Close. All other commands are restricted to usage in an an open ftp session. They will generate errors if they are used out of context. The ftp package includes file and directory manipulating commands for remote sites. To perform the same operations on the local site use commands built into the core, like cd or file.
The output of the package is controlled by two state variables, ::ftp::VERBOSE and ::ftp::DEBUG. Setting ::ftp::VERBOSE to "1" forces the package to show all responses from a remote server. The default value is "0". Setting ::ftp::DEBUG to "1" enables debugging and forces the package to show all return codes, states, state changes and "real" ftp commands. The default value is "0".
The command ::ftp::DisplayMsg is used to show the different messages from the ftp session. The setting of ::ftp::VERBOSE determines if this command is called or not. The current implementation of the command uses the log package of tcllib to write the messages to their final destination. This means that the behaviour of ::ftp::DisplayMsg can be customized without changing its implementation. For more radical changes overwriting its implementation by the application is of course still possible. Note that the default implementation honors the option -output to ::ftp::Open for a session specific log command.
Caution: The default implementation logs error messages like all other messages. If this behaviour is changed to throwing an error instead all commands in the API will change their behaviour too. In such a case they will not return a failure code as described below but pass the thrown error to their caller.
This command is used to start a FTP session by establishing a control connection to the FTP server. The defaults are used for any option not specified by the caller.
The command takes a host name server, a user name user and a password password as its parameters and returns a session handle that is an integer number greater than or equal to "0", if the connection is successfully established. Otherwise it returns "-1". The server parameter must be the name or internet address (in dotted decimal notation) of the ftp server to connect to. The user and passwd parameters must contain a valid user name and password to complete the login process.
The options overwrite some default values or set special abilities:
The blocksize is used during data transfer. At most size bytes are transfered at once. The default value for this option is 4096. The package will evaluate the -progress callback for the session after the transfer of each block.
If seconds is non-zero, then ::ftp::Open sets up a timeout which will occur after the specified number of seconds. The default value is 600.
The port number specifies an alternative remote port on the ftp server on which the ftp service resides. Most ftp services listen for connection requests on the default port 21. Sometimes, usually for security reasons, port numbers other than 21 are used for ftp connections.
The transfer mode option determines if a file transfer occurs in active or passive mode. In passive mode the client will ask the ftp server to listen on a data port and wait for the connection rather than to initiate the process by itself when a data transfer request comes in. Passive mode is normally a requirement when accessing sites via a firewall. The default mode is active.
This callback is evaluated whenever a block of data was transfered. See the option -blocksize for how to specify the size of the transfered blocks.
When evaluating the callback one argument is appended to the callback script, the current accumulated number of bytes transferred so far.
Specifying this option places the connection into asynchronous mode. The callback is evaluated after the completion of any operation. When an operation is running no further operations must be started until a callback has been received for the currently executing operation.
When evaluating the callback several arguments are appended to the callback script, namely the keyword of the operation that has completed and any additional arguments specific to the operation. If an error occurred during the execution of the operation the callback is given the keyword error.
This option has no default. If it is set the default implementation of ::ftp::DisplayMsg will use its value as command prefix to log all internal messages. The callback will have three arguments appended to it before evaluation, the id of the session, the message itself, and the connection state, in this order.
This command terminates the specified ftp session. If no file transfer is in progress, the server will close the control connection immediately. If a file transfer is in progress however, the control connection will remain open until the transfers completes. When that happens the server will write the result response for the transfer to it and close the connection afterward.
This command changes the current working directory on the ftp server to a specified target directory. The command returns 1 if the current working directory was successfully changed to the specified directory or 0 if it fails. The target directory can be
a subdirectory of the current directory,
Two dots, .. (as an indicator for the parent directory of the current directory)
or a fully qualified path to a new working directory.
This command returns the complete path of the current working directory on the ftp server, or an empty string in case of an error.
This command sets the ftp file transfer type to either ascii, binary, or tenex. The command always returns the currently set type. If called without type no change is made.
Currently only ascii and binary types are supported. There is some early (alpha) support for Tenex mode. The type ascii is normally used to convert text files into a format suitable for text editors on the platform of the destination machine. This mainly affects end-of-line markers. The type binary on the other hand allows the undisturbed transfer of non-text files, such as compressed files, images and executables.
This command returns a human-readable list of files. Wildcard expressions such as "*.tcl" are allowed. If pattern refers to a specific directory, then the contents of that directory are returned. If the pattern is not a fully-qualified path name, the command lists entries relative to the current remote directory. If no pattern is specified, the contents of the current remote directory is returned.
The listing includes any system-dependent information that the server chooses to include. For example most UNIX systems produce output from the command ls -l. The command returns the retrieved information as a tcl list with one item per entry. Empty lines and UNIX's "total" lines are ignored and not included in the result as reported by this command.
If the command fails an empty list is returned.
This command has the same behavior as the ::ftp::List command, except that it only retrieves an abbreviated listing. This means only file names are returned in a sorted list.
This command returns the size of the specified file on the ftp server. If the command fails an empty string is returned.
ATTENTION! It will not work properly when in ascii mode and is not supported by all ftp server implementations.
This command retrieves the time of the last modification of the file on the ftp server as a system dependent integer value in seconds or an empty string if an error occurred. Use the built-in command clock to convert the retrieves value into other formats.
This command deletes the specified file on the ftp server. The command returns 1 if the specified file was successfully deleted or 0 if it failed.
This command renames the file from in the current directory of the ftp server to the specified new file name to. This new file name must not be the same as any existing subdirectory or file name. The command returns 1 if the specified file was successfully renamed or 0 if it failed.
This command transfers a local file local to a remote file remote on the ftp server. If the file parameters passed to the command do not fully qualified path names the command will use the current directory on local and remote host. If the remote file name is unspecified, the server will use the name of the local file as the name of the remote file. The command returns 1 to indicate a successful transfer and 0 in the case of a failure.
If -data data is specified instead of a local file, the system will not transfer a file, but the data passed into it. In this case the name of the remote file has to be specified.
If -channel chan is specified instead of a local file, the system will not transfer a file, but read the contents of the channel chan and write this to the remote file. In this case the name of the remote file has to be specified. After the transfer chan will be closed.
This command behaves like ::ftp::Puts, but appends the transfered information to the remote file. If the file did not exist on the server it will be created.
This command retrieves a remote file remote on the ftp server and stores its contents into the local file local. If the file parameters passed to the command are not fully qualified path names the command will use the current directory on local and remote host. If the local file name is unspecified, the server will use the name of the remote file as the name of the local file. The command returns 1 to indicate a successful transfer and 0 in the case of a failure. The command will throw an error if the directory the file local is to be placed in does not exist.
If -variable varname is specified, the system will store the retrieved data into the variable varname instead of a file.
If -channel chan is specified, the system will write the retrieved data into the channel chan instead of a file. The system will not close chan after the transfer, this is the responsibility of the caller to ::ftp::Get.
This command behaves like ::ftp::Get, except that if local file local exists and is smaller than remote file remote, the local file is presumed to be a partially transferred copy of the remote file and the transfer is continued from the apparent point of failure. The command will throw an error if the directory the file local is to be placed in does not exist. This command is useful when transferring very large files over networks that tend to drop connections.
Specifying the additional byte offsets from and to will cause the command to change its behaviour and to download exactly the specified slice of the remote file. This mode is possible only if a local destination is explicitly provided. Omission of to leads to downloading till the end of the file.
This command behaves like ::ftp::Get, except that it retrieves the remote file only if the modification time of the remote file is more recent than the file on the local system. If the file does not exist on the local system, the remote file is considered newer. The command will throw an error if the directory the file local is to be placed in does not exist.
This command creates the specified directory on the ftp server. If the specified path is relative the new directory will be created as a subdirectory of the current working directory. Else the created directory will have the specified path name. The command returns 1 to indicate a successful creation of the directory and 0 in the case of a failure.
This command removes the specified directory on the ftp server. The remote directory has to be empty or the command will fail. The command returns 1 to indicate a successful removal of the directory and 0 in the case of a failure.
This command is used to send an arbitrary ftp command to the server. It cannot be used to obtain a directory listing or for transferring files. It is included to allow an application to execute commands on the ftp server which are not provided by this package. The arguments are sent verbatim, i.e. as is, with no changes.
In contrast to the other commands in this package this command will not parse the response it got from the ftp server but return it verbatim to the caller.
This command is used by the package itself to show the different messages from the ftp sessions. The package itself declares this command very simple, writing the messages to stdout (if ::ftp::VERBOSE was set, see below) and throwing tcl errors for error messages. It is the responsibility of the application to overwrite it as needed. A state variable for different states assigned to different colors is recommended by the author. The package log is useful for this.
A state variable controlling the output of the package. Setting ::ftp::VERBOSE to "1" forces the package to show all responses from a remote server. The default value is "0".
A state variable controlling the output of ftp. Setting ::ftp::DEBUG to "1" enables debugging and forces the package to show all return codes, states, state changes and "real" ftp commands. The default value is "0".
The correct execution of many commands depends upon the proper behavior by the remote server, network and router configuration.
An update command placed in the procedure ::ftp::DisplayMsg may run into persistent errors or infinite loops. The solution to this problem is to use update idletasks instead of update.
This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category ftp of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.