popclient(LOCAL)

. /* Copyright 1993-95 by Carl Harris, Jr. . * All rights reserved . * . * Distribute freely, except: don't remove my name from the source or . * documentation (don't take credit for my work), mark your changes (don't . * get me blamed for your possible bugs), don't alter or remove this . * notice. May be sold if buildable source is provided to buyer. No . * warrantee of any kind, express or implied, is included with this . * software; use at your own risk, responsibility for damages (if any) to . * anyone resulting from the use of this software rests entirely with the . * user. . * . * Send bug reports, bug fixes, enhancements, requests, flames, etc., and . * I'll try to keep a version up to date. I can be reached as follows: . * Carl Harris <ceharris@vt.edu> . */ . . $Log: popclient.man,v $ . Revision 1.4 1995/09/07 22:53:49 ceharris . One last bit of crap before the 3.0b4 release . . Revision 1.3 1995/08/14 18:36:46 ceharris . Patches to support POP3's LAST command. . Final revisions for beta3 release. . . Revision 1.2 1995/08/08 01:01:29 ceharris . Added GNU-style long options processing. . Fixed password in 'ps' output problem. . Fixed various RCS tag blunders. . Integrated .poprc parser, lexer, etc into Makefile processing. . .

NAME
popclient - retrieve mail from a mailserver using Post Office Protocol.

SYNOPSIS
popclient [ options ] server-host [server-host...]

DESCRIPTION
popclient is a Post Office Protocol compliant mail retrieval client which supports both POP2 (as specified in RFC 937) and POP3 (RFC 1725).

Typically, popclient will be used to download mail in batch from the remote mailserver specified by host to a mail folder on the local disk. The retrieved mail will then be manipulated using a local mail reader, such as mail or elm.

To facilitate the use of popclient in scripts, pipelines, etc, it returns an appropriate exit code upon termination -- see EXIT CODES below.

OPTIONS

-2  Use Post Office Protocol version 2 (POP2). See also the --protocol option, below.

-3  Use Post Office Protocol version 3 (POP3). See also the --protocol option, below.

-a, --all
    POP3 only. Retrieve both old (previously retrieved) and new messages from the mailserver.

-c, --stdout
    Causes retrieved messages to be written to stdout instead of a mail folder. See OUTPUT OPTIONS below for a complete description. You may not specify both the -c and -o options on the same command line.

-F, --flush
    POP3 only. Delete old (previously retrieved) messages from the mailserver before retrieving new messages.

-f pathname, --poprc pathname
    Specify an alternate name for the .poprc file.

-k, --keep
    Keep retrieved messages in folder on remote mailserver. Normally, messages are deleted from the folder on the mailserver after they have been retrieved (unless popclient was compiled with the KEEP_IS_DEFAULT option). Specifying the keep option causes retrieved messages to remain in your folder on the mailserver.

-K, --kill
    Delete retrieved messages from the remote mailserver. If popclient is compiled with the KEEP_IS_DEFAULT option, the kill option forces retrieved mail to be deleted.

-l lines, --limit lines
    POP3 only. Retrieve no more than the specified number of lines of each message body (plus message headers). The keep option is implied by the limit option -- i.e. messages downloaded with the limit option remain on the remote mailserver.

-p string, --password string
    Specifies the password string to be used when logging-in to the mailserver. The appropriate password is both server and user dependent. If the password option is not used to specify a password, you will be prompted for a password before the connection to the mailserver is established. See USER AUTHENTICATION below for a complete description.

--protocol proto
    Specify the protocol to used when communicating with the remote mailserver. proto may be one of the following:

    POP2
        Post Office Protocol 2

    POP3
        Post Office Protocol 3

    APOP
        Use POP3 with MD5 authentication.

    RPOP
        Use POP3 with trusted-host-based authentication (like rlogin/rsh). popclient must be installed as a setuid root program to use RPOP. --proto.

-o folder, --local folder
    Causes retrieved messages to be appended to file named by the folder argument. When neither -o nor -c is specified, retrieved messages are appended to the system default mail folder. See OUTPUT OPTIONS below for a complete description.

-r folder, --remote folder
    Causes an alternate mail folder on the mailserver to be retrieved. The syntax of the folder name is server dependent, as is the default behavior when no folder is specified. Fortunately, most POP servers have a reasonable default behavior, so use of this option should be limited to fairly specialized applications. POP3 does not provide a folder specification in the protocol. If the remote option is used in conjunction with the POP3 protocol, the remote folder specification is ignored.

-s, --silent
    Silent mode. Suppresses all progress/status messages that are normally echoed to stderr during a POP connection. If both the silent and verbose options are specified, the verbose option takes precedence.

-u name, --username name
    Specifies the user idenfication to be used when logging-in to the mailserver. The appropriate user identification is both server and user dependent. The default is your login name on the machine that is running popclient. See USER AUTHENTICATION below for a complete description.

-v, --verbose
    Verbose mode. All control messages passed between popclient and the mailserver are echoed to stderr. Specifying verbose causes normal progress/status messages which would be redundant or meaningless to be modified or omitted.

-V, --version
    Displays the version information for your copy of popclient. If you specify the version option, all other options are ignored and no POP connection is made.

PROTOCOL SELECTION
The selection of the correct Post Office Protocol (POP2 or POP3) depends upon the configuration of the mailserver from which you retrieve your mail. The system adminstrator who installed popclient on your system should have chosen an appropriate default protocol for your mailserver. If you get the message 'Connection refused' when using the default protocol, try specifying -2 or -3 to select a different protocol. If the 'Connection refused' message persists regardless of the protocol selected, it is likely that your mailserver is not running a POP compliant mail service.

USER AUTHENTICATION
User authentication in popclient is very much like the authentication mechanism of ftp(1). The correct user-id and password depend upon the underlying security system at the mailserver.

If the mailserver is a Unix machine on which you have an ordinary user account, your regular login name and password are used with popclient. If you use the same login name on both the server and the client machines, you needn't worry about specifying a user-id with the -u option -- the default behavior will use your login name on the client machine as the user-id on the server machine. If you use a different login name on the server machine, specify that login name with the -u option. e.g. if your login name is 'jsmith' on a machine named 'mailgrunt', you would start popclient as follows:

    popclient -u jsmith mailgrunt

The default behavior of popclient is to prompt you for your mailserver password before the POP connection is established. This is the safest way to use popclient and ensures that your password will not be compromised. You may also specify your password using the -p option. This is convenient when using popclient with automated scripts, but it may result in your password being exposed to prying eyes -- be careful! Regardless of how your password is specified it is never stored in shared memory segments, or left unencrypted in the core image when popclient terminates. Continuing the preceding example, suppose your password on 'mailgrunt' is 'Gr8PassWd'. The syntax would be:

    popclient -u jsmith -p Gr8PassWd mailgrunt

On mailservers that do not provide ordinary user accounts, your user-id and password are usually assigned by the server administrator when you apply for a mailbox on the server. Contact your server administrator if you don't know the correct user-id and password for your mailbox account.

OUTPUT OPTIONS
popclient always writes the retrieved messages using Unix mail folder format. This allows popclient to be used in conjunction with common mail readers like mail and elm. The retrieved messages are normally appended to your default system mailbox on the local disk, using the local Mail Delivery Agent (MDA), usually /bin/mail(1), so that when you invoke your mail reader it can manipulate the retrieved messages like any other mail you receive on the client machine.

Using the -o option, you can specify a different mail folder to which the retrieved messages will be appended. If you prefer, for example, to have your POP mail from a machine called 'mailgrunt' stored in the mbox file in your home directory, you would start popclient as follows:

    popclient -o $HOME/mbox mailgrunt

Note that the folder specified with -o is not locked or otherwise protected from other processes writing to it while popclient is writing to it.

popclient can be used in a shell pipeline by using the -c option. In this mode, popclient writes the retrieved messages to stdout, instead of a mail folder. This would allow you, for instance, to pass the incoming mail through a filter that discards mail marked as 'Precedence: junk'. Suppose you've written an AWK script called 'dumpjunk.awk' to implement a junk mail filter. The appropriate syntax to retrieve your mail from 'mailgrunt', pass it through the filter, and write it to a folder called 'realmail' in your home directory would be:

    popclient -c mailgrunt | awk -f dumpjunk.awk > $HOME/realmail

The progress/status messages written to stderr when the -s option has not been specified, do not interfere with the message stream, which is written to stdout. You may even use -v and -c together without corrupting the message stream. It is a good idea to use the -k option when using -c to insure that your messages will not be lost if part of the shell pipeline does not function incorrectly. The safest bet would be something like:

    popclient -k -c mailgrunt | myfilter > $HOME/filtered.mail

followed by

    popclient -c mailgrunt > /dev/null

when you're sure the messages were correctly processed by 'myfilter'.

EXIT CODES
To facilitate the use of popclient in shell scripts and the like, an exit code is returned to give an indication of what occured during a given POP connection. The exit code can be tested by the script and appropriate action taken.

A simple example follows. This Bourne shell script executes popclient and, if some messages were successfully retrieved from a mailserver retrieved from the command line, it starts the mail utility to read those messages. Otherwise, it prints a brief message, and exits.
    #!/bin/sh
    if popclient $1
    then
      mail
    else
      echo "No mail to read."
    fi

The exit codes returned by popclient are as follows:

0   One or more messages were successfully retrieved.

1   There was no mail awaiting retrieval.

2   An error was encountered when attempting to open a socket for the POP connection. If you don't know what a socket is, don't worry about it -- just treat this as an 'unrecoverable error'.

3   The user authentication step failed. This usually means that a bad user-id or password was specified.

4   Some sort of protocol error was detected. POP is not especially forgiving when it comes to unexpected responses, commands, etc -- the protocol invariably calls for terminating the connection under such error conditions.

5   There was a syntax error in the arguments to popclient.

6   Some kind of I/O woes occurred when writing to the local folder.

7   There was an error condition reported by the server (POP3 only).

9   Something totally undefined occured. This is usually caused by a bug within popclient. Do let me know if this happens.

AUTHOR
popclient was written by Carl Harris at Virginia Polytechnic Institute and State University (a.k.a. Virginia Tech).

BUGS
There are none! Well, maybe one or two. Send comments, bug reports, gripes, and the like to ceharris@mal.com.

SEE ALSO
mail(1), binmail(1), sendmail(8), popd(8), RFC 937, RFC 1225.