SZ, Zmodem Send
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SZ, Zmodem Send
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NAME
sz - ZMODEM file send
zcommand, zcommandi - ZMODEM command download
SYNOPSIS
sz [-+abdEefgIikLlMmNnoPpqtuvxyYZ] file ...
zcommand [-oqtv] COMMAND
zcommandi [-oqtv] COMMAND
sz -T
DESCRIPTION
This set of commands uses the ZMODEM, YMODEM or XMODEM error
correcting protocol to send files to a program logged into a
serial port. (See NETWORK NOTES, below.)
This version of sz operates with Omen Technology products,
and is licensed only for use therewith.
Commercial sz and rz for use with any program supporting
XMODEM, YMODEM, or ZMODEM are available for purchase from
Omen Technology INC.
The program is not designed be called from cu, tip, kermit,
or any other communications program. Unix flavors of Omen
Technology's Professional-YAM communications software are
available for dial-out applications.
Sz sends one or more files with ZMODEM protocol.
Zcommand sends a single COMMAND to a ZMODEM receiver for
execution. Zcommand exits with the COMMAND return value.
If COMMAND includes spaces or characters special to the
shell, it must be quoted.
Zcommandi sends a single COMMAND to a ZMODEM receiver for
execution. Zcommandi exits as soon as the receiver has
correctly received the command, before it is executed.
The sixth form (sz -T) outputs all 256 code combinations to
the terminal. The hex value of the character, a space, and
the raw character are sent, 8 per line. In you are having
difficulty sending files, this command lets you see which
character codes are being eaten or corrupted by the
operating system or network. The terminal program must be
set to display all 256 codes in a distinct form. Check that
each code is sent, and that the 8th bit on codes 0x80 to
0xFF is set.
Sz -T then allows the caller to input characters which are
echoed in hex. You should check that all control characters
can be input this way.
The meanings of the available options are:
\ (backslash) (VMS) Force the next option letter to upper
case.
+ Instruct the receiver to append transmitted data to an
existing file (ZMODEM only).
a Instruct the ZMODEM receiver to convert text file
format as appropriate for the receiving system. When
sending to a PC-DOS system, the receiving ZMODEM
program converts END OF LINE to a CR/LF pair.
b (ZMODEM) Binary override: transfer file without any
translation.
bb (bogus binary) On VMS reads disk files with an
alternate mode. Suitable for a few strange file types
such as Lotus .wk3 spreadsheet files.
d Change all instances of "." to "/" in the transmitted
pathname. Thus, C.omenB0000 (which is unacceptable to
MSDOS or CP/M) is transmitted as C/omenB0000. If the
resultant filename has more than 8 characters in the
stem, a "." is inserted to allow a total of eleven.
e Escape all control characters; normally XON, XOFF, DLE,
CR-@-CR, and Ctrl-X are escaped.
E Escape the 8th bit to allow operation over 7 bit paths.
Witnout the P option, data is compressed.
EP Pack 4 data bytes into 5 bytes for operation over 7 bit
paths. This is more efficient when the data is already
compressed.
f Send Full pathname. Normally directory prefixes are
stripped from the transmitted filename.
ff Send Full VMS pathname including device name and
version number.
g Send ESC-[-?-3-4-l to start DSZ from Kermit.
i Make VMS receiver use Stream_LF record format to avoid
padding file with nulls. This record format is
understood by many C programs.
I Make VMS receiver use Variable length (mrs=510) image
record format to avoid padding file with nulls. This
binary record format is understood by many Kermit
programs.
LN Use ZMODEM sub-packets of length N. A larger N (32 <=
N <= 1024) gives slightly higher throughput, a smaller
N speeds error recovery. The default is 128 below 300
baud, 256 above 300 baud, or 1024 above 2400 baud.
lN Wait for the receiver to acknowledge correct data every
N (32 <= N <= 1024) characters. This may be used to
avoid network overrun when XOFF flow control is
lacking.
m Request MobyTurboTm throughput enhancement.
M Lock out MobyTurboTm throughput enhancement.
n (ZMODEM) Send each file if destination file does not
exist. Overwrite destination file if source file is
newer than the destination file.
N (ZMODEM) Send each file if destination file does not
exist. Overwrite destination file if source file is
newer or longer than the destination file.
o (ZMODEM) Disable automatic selection of 32 bit CRC.
p (ZMODEM) Protect existing destination files by skipping
transfer if the destination file exists.
q When sz starts up, sz counts the files to be sent and
totals their lengths. This information allows the
receiver to display the progress in a multiple file
(batch) transmission. When many files are specified
(as with wild cards) this takes some time. The q
(quiet) option bypasses this count.
r (ZMODEM) Resume interrupted file transfer. If the
source file is longer than the destination file, the
transfer commences at the offset in the source file
that equals the length of the destination file.
rr As above, but compares the files (the portion common to
sender and receiver) before resuming the transfer.
ttim Change timeout to tim tenths of seconds.
u Unlink the file after successful transmission. Users
should not manually abort or skip file transfers when
this option is used.
wN Limit the transmit window size to N bytes (ZMODEM).
The sz program will interrogate the receiver and pause
if necessary to let the receiver catch up to within the
specified window size. This option is useful when
sending long files over networks that time out if the
user does not enter commands frequently.
v Verbose causes a list of file names to be appended to
/tmp/szlog (szlog.tmp on VMS). More v's generate more
detailed output.
x Count skipped files as errors.
y Instruct a ZMODEM receiving program to overwrite any
existing file with the same name.
Y Instruct a ZMODEM receiving program to overwrite any
existing file with the same name, and to skip any
source files that do have a file with the same pathname
on the destination system.
Z Use ZMODEM file compression to speed file transfer.
DIAGNOSTICS
Exit status is as follows: 0 for successful transfers. 1 if
unrecoverable errors are detected. 2 if syntax errors or
file access problems are detected. 3 if the program was
terminated by a caught interrupt.
EXAMPLES
ZMODEM File Transfer (Unix to DSZ/ZCOMM/Professional-YAM)
% sz -a *.c
This single command transfers all .c files in the current
Unix directory with conversion (-a) to end of line
conventions appropriate to the receiving environment. With
ZMODEM AutoDownload enabled, Professional-YAM and ZCOMM
will automatically receive the files after performing a
security check.
% sz -Yan *.c *.h
Send only the .c and .h files that exist on both systems,
and are newer on the sending system than the corresponding
version on the receiving system, converting Unix to DOS text
format.
$ sz "-Yan" file1.c file2.c file3.c foo.h baz.h (for VMS)
ZMODEM Command Download (Unix to Professional-YAM)
cpszall:all
zcommand "c:;cd /yam/dist"
sz -ya $(YD)/*.me
sz -yqb y*.exe
zcommand "cd /yam"
zcommandi "!insms"
This Makefile fragment uses zcommand to issue commands to
Professional-YAM to change current disk and directory.
Next, sz transfers the .me files from the $YD directory,
commanding the receiver to overwrite the old files and to
convert from Unix end of line conventions to PC-DOS
conventions. The third line transfers some .exe files. The
fourth and fifth lines command Pro-YAM to change directory
and execute a PC-DOS batch file insms . Since the batch file
takes considerable time, zcommandi form is used to allow sz
to exit immediately.
XMODEM File Transfer (Unix to Crosstalk)
% sx foo.c
ESC
rx foo.c
The above three commands transfer a single file from Unix to
a PC and Crosstalk. This combination is much slower and
less reliable under stress than ZMODEM.
NOTES
ZMODEM greatly simplifies file transfers compared to XMODEM.
In addition to a friendly user interface, ZMODEM provides
Personal Computer and other users an efficient, accurate,
and robust file transfer method.
ZMODEM provides complete END-TO-END data integrity between
application programs. ZMODEM's 32 bit CRC catches errors
that sneak into even the most advanced networks.
Advanced file management features include AutoDownload
(Automatic file Download initiated without user
intervention), Display of individual and total file lengths
and transmission time estimates, Crash Recovery, selective
file transfers, and preservation of exact file date and
length.
The -y option instructs the receiver to open the file for
writing unconditionally. The -a option causes the receiver
to convert Unix newlines or VMS variable length records to
the receiving system's standard text format (carriage
returns and linefeeds for PC-DOS).
On VMS and Unix systems, sz and sb send the length and date
of each file. If the receiving program uses this
information, the transmitted file length controls the exact
number of bytes written to the output dataset, and the
modify time and file mode are set accordingly.
SERVER/NETWORK NOTES
Terminals on some timesharing systems are connected
indirectly to the host with TERMINAL SERVERS operating over
networks. Terminal servers often interfere with file
transfers by "eating" control characters and/or losing data.
When terminal servers interfere with file transfers, server
commands are often available to help the problem. When
possible, enable the server and modems for hardware flow
control in and out. Set the terminal server to telnet
transparent mode. Some typical commands are "SET TERMINAL
DOWNLOAD", "set session passall", and "SET TERMINAL NO ESC",
but there is no standard set of commands suitable for all
terminal servers. Normally these commands are given before
attempting file transfers, but one user has reported that
the command must be given after the file transfer is
started(!). Until terminal server vendors improve the
quality of their product, you may have to get on their case
until they adequately support high performance file
transfers.
Escaping control characters (sz -e) may help if the transfer
gets stuck in the same place on every attempt.
Professional-YAM and ZCOMM allow selection of which control
characters need to be escaped. In extreme cases 7-bit
transmission may be required (see the Professional-YAM/ZCOMM
manual).
If you encounter problems with control characters Please
refer to the sz -T command in sz.doc for more help.
Flow control between the server and modem is often
defective. This rarely causes a problem in interactive
applications whose short bursts (a screenfull at most) fit
within the available memory buffers. Streaming protocols
such as YMODEM-g, long packet SuperKermit, and ZMODEM can
overload the available buffering. Some terminal servers
support commands to enable hardware flow control such as
"TERM FLOWCONTROL HARDWARE IN OUT"; this assumes the modem
attached to the server is properly configured.
If the terminal server is too brain damaged to support flow
control, you can fake it with ZMODEM. Try
sz -w1024 file...
to enable software flow control. Experiment with different
values to find the best throughput.
Terminal servers are designed to accept keyboard input from
human operators. They may lose data when a program sends
data to the host faster than humans type. Some servers
allow larger input buffers to support file uploads. If you
can upload short files (less than 100 bytes) but not longer
files, try
sz -w1024 file...
with your uploading program. (Not all programs support this
option; use ZCOMM or Professional-YAM.)
When both flow control and character transparency are
problems, use
sz -ew1024 file...
as a starting point.
Sometimes the terminal server software is defective and must
be upgraded. Please contact the network's vendor for
corrective procedures. An alternative is to install direct
serial ports for users desiring to upload files.
Some systems enforce a timeout which disconnects a user
after several minutes of no keyboarding. This can cause
problems in long, error free ZMODEM transfers. Restricting
the window size with a "-w8192" option provides terminal
input at regular intervals even when no error correction is
needed. If problems persist, try setting a packet length.
sz -l1024 file...
(The default ZMODEM packet length is the file length.)
SEE ALSO
Professional-YAM, rz(omen), crc(omen), sq(omen),
todos(omen), tocpm(omen), tomac(omen)
VMS NOTES
To use sz a DCL verb must be defined with syntax similar to
the following:
sz :== "$disk$user2:[username.subdir]sz.exe sz"
For example, if "dir sz" results in:
Directory SYS$SYSDEVICE:[CAF]
SZ.EXE;41
then you should define sz:
$sz :== "$sys$sysdevice:[CAF]vsz.exe sz"
Other verbs are:
$zcommand :== "$sys$sysdevice:[CAF]vsz.exe zcommand"
$zcommandi :== "$sys$sysdevice:[CAF]vsz.exe zcommandi"
Wild cards are expanded within sz.
sz -a [*...]*.h sends all accessible .h files in the system.
VMS DCL forces command line arguments to upper case unless
they are enclosed by double quotes. Upper case option
letters may be represented by preceding the letter with \.
VMS C Standard I/O and RMS may interact to modify the file
contents. File lengths are not accurately reported for some
VMS record formats; When files are sent with XMODEM or
YMODEM, file length is measured by counting the characters
therein.
For efficient operation at high baud rates, the system
manager should "set term tta0:/altypeahd/perm" (choose the
appropriate tty port). This must be done when the
particular terminal line is not logged in. Without setting
altypeahd you may get excessive retries and/or lousy
throughput.
In addition the system manager can try increasing the SYSGEN
parameter TTY_TYPAHDSZ to, say, 2048 or more.
In order to get the maximum speed the process quotas
buffered I/O byte count should be 30000 or more and buffered
I/O limit should be 100 or more.
To see what you have type:
$ show process/quotas
To change this type:
$ set default sys$system
$ run authorize
modify/BIOlm=100/Bytlm=30000 caf (or whatever your
username is)
exit
Now log out and log back in to get the new quotas.
UNIX NOTES
Iff sz is invoked with $SHELL set and iff that variable
contains the string rsh or rksh (restricted shell), sz
operates in restricted mode. Restricted mode restricts
pathnames to the current directory and PUBDIR (usually
/usr/spool/uucppublic) and/or subdirectories thereof.
FILES
/tmp/szlog stores debugging output (sz -vv) (SZLOG.TMP on
VMS).
32 bit CRC code courtesy Gary S. Brown.
TESTING FEATURE
The command "sz -T file" exercises the Attn sequence error
recovery by commanding errors with unterminated packets.
The receiving program should complain five times about
binary data packets being too long. Each time sz is
interrupted, it should send a ZDATA header followed by
another defective packet. If the receiver does not detect
five long data packets, the Attn sequence is not
interrupting the sender, and the Myattn string in sz.c must
be modified.
After 5 packets, sz stops the "transfer" and prints the
total number of characters "sent" (Tcount). The difference
between Tcount and 5120 represents the number of characters
stored in various buffers when the Attn sequence is
generated.
NOTES
Sz is not designed be called from cu(1) or other outdial
communications programs. Unix and VMS flavors of Omen
Technology's Professional-YAM communications software are
available for dial-out applications.
When using TrailBlazer or other buffered modems at high
speed, particular attention must be paid to flow control.
The modem and Unix must agree on the flow control method.
Sz on USG (SYS III/V) systems uses XON/XOFF flow control.
If flow control cannot be properly set up, Try a "-w2048"
option to enforce protocol level flow control. Experiment
with different window sizes for best results.
Telebit modems must not be set to "spoof" UUCP, XMODEM, or
KERMIT. Setting one of these spoofing modes interferes with
other protocols.
Circular buffering and a ZMODEM sliding window should be
used when input is from pipes instead of acknowledging
frames each 1024 bytes. If no files can be opened, sz sends
a ZMODEM command to echo a suitable complaint; perhaps it
should check for the presence of at least one accessible
file before getting hot and bothered.
A few high speed modems have a firmware bug that drops
characters when the direction of high speed transmission is
reversed. The environment variable ZNULLS may be used to
specify the number of nulls to send before a ZDATA frame.
Values of 101 for a 4.77 mHz PC and 124 for an AT are
typical.
BUGS
On at least one BSD system, sz would abend it got within a
few kilobytes of the end of file. Using the "-w8192" flag
fixed the problem. The real cause is unknown, perhaps a bug
in the kernel TTY output routines.
The test mode leaves a zero length file on the receiving
system.
LICENSE
Use of this software for commercial or administrative
purposes except when exclusively limited to interfacing Omen
Technology products requires a license from Omen Technology
Inc. Use of this code by inclusion, decompilation, reverse
engineering or any other means constitutes agreement to
these conditions and acceptance of liability to license the
materials and payment of any reasonable legal or
investigative costs necessary to enforce this license
agreement.
Copyright 1993 Omen Technology INC All Rights Reserved
Omen Technology INC
Post Office Box 4681
Portland OR 97208
503-621-3406
Information Services, Central Computing
University
of Missouri Kansas City