Ubuntu Manpage: sx, sb, sz - XMODEM, YMODEM, ZMODEM file send

NAME

       sx, sb, sz - XMODEM, YMODEM, ZMODEM file send

SYNOPSIS

       sz [-+8abdefkLlNnopqTtuvyY] file ...
       sb [-adfkqtuv] file ...
       sx [-akqtuv] file
       sz [-oqtv] -c COMMAND
       sz [-oqtv] -i COMMAND
       sz -TT

DESCRIPTION

Sz uses the ZMODEM, YMODEM or XMODEM error correcting protocol to send one or more files over a dial-in
serial port to a variety of programs running under PC-DOS, CP/M, Unix, VMS, and other operating systems.

While rz is smart enough to be called from cu(1), very few versions of cu(1) are smart enough to allow sz
to work properly. Unix flavors of Professional-YAM are available for such dial-out application.

Sz sends one or more files with ZMODEM protocol.

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.

Output from another program may be piped to sz for transmission by denoting standard input with "-":
ls -l | sz -
The program output is transmitted with the filename sPID.sz where PID is the process ID of the sz
program. If the environment variable ONAME is set, that is used instead. In this case, the Unix
command:
ls -l | ONAME=con sz -ay -
will send a "file" to the PC-DOS console display. The -y option instructs the receiver to open the file
for writing unconditionally. The -a option causes the receiver to convert Unix newlines to PC-DOS
carriage returns and linefeeds.

Sb batch sends one or more files with YMODEM or ZMODEM protocol. The initial ZMODEM initialization is
not sent. When requested by the receiver, sb supports YMODEM-g with "cbreak" tty mode, XON/XOFF flow
control, and interrupt character set to CAN (^X). YMODEM-g (Professional-YAM g option) increases
throughput over error free channels (direct connection, X.PC, etc.) by not acknowledging each
transmitted sector.

On Unix systems, additional information about the file is transmitted. 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.

Sx sends a single file with XMODEM or XMODEM-1k protocol (sometimes incorrectly called "ymodem"). The
user must supply the file name to both sending and receiving programs.

If sz is invoked with $SHELL set and iff that variable contains the string rsh , rbash 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.

The fourth form sends a single COMMAND to a ZMODEM receiver for execution. Sz exits with the COMMAND
return value. If COMMAND includes spaces or characters special to the shell, it must be quoted.

The fifth form sends a single COMMAND to a ZMODEM receiver for execution. Sz exits as soon as the
receiver has correctly received the command, before it is executed.

The sixth form (sz -TT) attempts to output all 256 code combinations to the terminal. In you are having
difficulty sending files, this command lets you see which character codes are being eaten by the
operating system.

If sz is invoked with stdout and stderr to different datasets, Verbose is set to 2, causing frame by
frame progress reports to stderr. This may be disabled with the q option.

The meanings of the available options are:

-+, --append
Instruct the receiver to append transmitted data to an existing file (ZMODEM only).
-2, --twostop
use two stop bits (if possible). Do not use this unless you know what you are doing.
-8, --try-8k
Try to go up to 8KB blocksize. This is incompatible with standard zmodem, but a common extension
in the bbs world. (ZMODEM only).
--start-8k
Start with 8KB blocksize. Like --try-8k.
-a, --ascii
Convert NL characters in the transmitted file to CR/LF. This is done by the sender for XMODEM and
YMODEM, by the receiver for ZMODEM.
-b, --binary
(ZMODEM) Binary override: transfer file without any translation.
-B NUMBER, --bufsize NUMBER
Use a readbuffer of NUMBER bytes. Default ist 16384, which should be enough for most situations.
If you have a slow machine or a bad disk interface or suffer from other hardware problems you
might want to increase the buffersize. -1 or auto use a buffer large enough to buffer the whole
file. Be careful with this option - things normally get worse, not better, if the machine starts
to swap.

Using this option turns of memory mapping of the input file. This increases memory and cpu usage.
-c COMMAND, --command COMMAND
Send COMMAND to the receiver for execution, return with COMMAND´s exit status.
-C N, --command-tries N
Retry to send command N times (default: 11).
-d, --dot-to-slash
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.

This option enables the --full-path option.
--delay-startup N
Wait N seconds before doing anything.
-e, --escape
Escape all control characters; normally XON, XOFF, DLE, CR-@-CR, and Ctrl-X are escaped.
-E, --rename
Force the sender to rename the new file if a file with the same name already exists.
-f, --full-path
Send Full pathname. Normally directory prefixes are stripped from the transmitted filename.

This is also turned on with to --dot-to-slash option.
-h, --help
give help.
-i COMMAND, --immediate-command COMMAND
Send COMMAND to the receiver for execution, return immediately upon the receiving program's
successful reception of the command.
-k, --1k
(XMODEM/YMODEM) Send files using 1024 byte blocks rather than the default 128 byte blocks. 1024
byte packets speed file transfers at high bit rates. (ZMODEM streams the data for the best
possible throughput.)
-L N, --packetlen N
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.
-m N, --min-bps N
Stop transmission if BPS-Rate (Bytes Per Second) falls below N for a certain time (see --min-bps-
time option).
-M N, --min-bps-time
Used together with --min-bps. Default is 120 (seconds).
-l N, --framelen N
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.
-n, --newer
(ZMODEM) Send each file if destination file does not exist. Overwrite destination file if source
file is newer than the destination file.
-N, --newer-or-longer
(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, --16-bit-crc
(ZMODEM) Disable automatic selection of 32 bit CRC.
-O, --disable-timeouts
Disable read timeout handling. This makes lsz hang if the other side doesn't send anything, but
increases performance (not much) and decreases system load (reduces number of system calls by
about 50 percent).

Use this option with care.
-p, --protect
(ZMODEM) Protect existing destination files by skipping transfer if the destination file exists.
-q, --quiet
Quiet suppresses verbosity.
-R, --restricted
Restricted mode: restricts pathnames to the current directory and PUBDIR (usually
/usr/spool/uucppublic) and/or subdirectories thereof.
-r, --resume
(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.
-s HH:MM, --stop-at HH:MM
Stop transmission at HH hours, MM minutes. Another variant, using +N instead of HH:MM, stops
transmission in N seconds.
-S, --timesync
enable timesync protocol support. See timesync.doc for further information.

This option is incompatible with standard zmodem. Use it with care.
--syslog[=off]
turn syslogging on or off. the default is set at configure time. This option is ignored if no
syslog support is compiled in.
-t TIM, --timeout TIM
Change timeout to TIM tenths of seconds.
-T, --turbo
Do not escape certain characters (^P, ^P|0x80, telenet escape sequence [CR + @]). This improves
performance by about 1 percent and shouldn't hurt in the normal case (but be careful - ^P might be
useful if connected through a terminal server).
--tcp Try to initiate a TCP/IP connection. lsz will ask the receiving zmodem to open a TCP/IP
connection. All handshaking (which address / port to use) will be done by the zmodem programs.

You will normally not want to use this option as lrzsz is the only zmodem which understands what
to do (private extension). You might want to use this option if the two programs are connected
(stdin/out) over a slow or bad (not 8bit clean) network connection.

Use of this option imposes a security risk, somebody else could connect to the port in between.
See SECURITY for details.
--tcp-client ADDRESS:PORT
Act as a tcp/ip client: Connect to the given port.

See --tcp-server for more information.

--tcp-server
Act as a server: Open a socket, print out what to do, wait for connection.

You will normally not want to use this option as lrzsz is the only zmodem which understands what
to do (private extension). You might want to use this if you have to use zmodem (for which reason
whatever), and cannot use the --tcp option of lsz (perhaps because your telnet doesn't allow to
spawn a local program with stdin/stdout connected to the remote side).

If you use this option you have to start lsz with the --tcp-client ADDRESS:PORT option. lrz will
print the address and port on startup.

Use of this option imposes a security risk, somebody else could connect to the port in between.
See SECURITY for details.

-u Unlink the file after successful transmission.
-U, --unrestrict
Turn off restricted mode (this is not possible if running under a restricted shell).
-w N, --windowsize N
Limit the transmit window size to N bytes (ZMODEM).
-v, --verbose
Verbose output to stderr. More v's generate more output.
-X, --xmodem
use XMODEM protocol.
-y, --overwrite
Instruct a ZMODEM receiving program to overwrite any existing file with the same name.
-Y, --overwrite-or-skip
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.
--ymodem
use ZMODEM protocol.
-Z, --zmodem
use ZMODEM protocol.

SECURITY

       Restricted mode restricts pathnames to the current directory and PUBDIR  (usually  /var/spool/uucppublic)
       and/or subdirectories thereof, and disables remote command execution.

       Restricted  mode  is  entered  if the R option is given or if lsz detects that it runs under a restricted
       shell or if the environment variable ZMODEM_RESTRICTED is found.

       Restricted mode can be turned of with the U option if not running under a restricted shell.

       Use of the
              --tcp-client or --tcp-server options imposes a security risk, as somebody else  could  connect  to
              the  port  before you do it, and grab your data. If there's strong demand for a more secure mode i
              might introduce some sort of password challenge.

ENVIRONMENT

       ZNULLS may be used to specify the number of nulls to send before a ZDATA frame.

       SHELL  lsz recognizes a restricted shell if this variable includes rsh or rksh

       ZMODEM_RESTRICTED
              lrz enters restricted mode if the variable is set.

       TMPDIR If this environment variable is set its content is used as the directory to place  in  the  answer
              file  to  a  timesync request.  TMP Used instead of TMPDIR if TMPDIR is not set. If neither TMPDIR
              nor TMP is set /tmp will be used.

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
           sz -c "c:;cd /yam/dist"
           sz -ya $(YD)/*.me
           sz -yqb y*.exe
           sz -c "cd /yam"
           sz -i "!insms"
       This  Makefile  fragment  uses  sz  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, the -i form is used to allow sz
       to exit immediately.

       XMODEM File Transfer (Unix to Crosstalk)
       % sx -a foo.c
       ESC
       rx foo.c
       The above three commands transfer a single file from Unix to a PC and Crosstalk with sz translating  Unix
       newlines to DOS CR/LF.  This combination is much slower and far less reliable than ZMODEM.

ERROR MESSAGES

       "Caught  signal  99"  indicates  the program was not properly compiled, refer to "bibi(99)" in rbsb.c for
       details.

VMS VERSION

       The  VMS  version  does  not  support  wild cards.  Because of VMS DCL, upper case option letters must be
       represented by \ preceding the letter.

       The current VMS version does not support XMODEM, XMODEM-1k, or YMODEM.

       VMS C Standard I/O and RMS may interact to modify the file contents.

FILES

       32 bit CRC code courtesy Gary S. Brown.

       sz.c, crctab.c, rbsb.c, zm.c, zmodem.h Unix source files

       sz.c, crctab.c, vrzsz.c, zm.c, zmodem.h, vmodem.h, vvmodem.c, VMS source files.

       /tmp/szlog stores debugging output (sz -vv) (szlog on VMS).

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.

BUGS

Calling sz from most versions of cu(1) doesn't work because cu's receive process fights sz for characters
from the modem.

On at least one BSD system, sz would hang or exit when it got within a few kilobytes of the end of file.
Using the "-w 8192" flag fixed the problem. The real cause is unknown, perhaps a bug in the kernel TTY
output routines.

Programs that do not properly implement the specified file transfer protocol may cause sz to "hang" the
port for a minute or two. This problem is corrected by using ZCOMM, Pro-YAM, or other program with a
correct implementation of the specified protocol.

Many programs claiming to support YMODEM only support XMODEM with 1k blocks, and they often don't get
that quite right.

XMODEM transfers add up to 127 garbage bytes per file. XMODEM-1k and YMODEM-1k transfers use 128 byte
blocks to avoid extra padding.

YMODEM programs use the file length transmitted at the beginning of the transfer to prune the file to the
correct length; this may cause problems with source files that grow during the course of the transfer.
This problem does not pertain to ZMODEM transfers, which preserve the exact file length unconditionally.

Most ZMODEM options are merely passed to the receiving program; some do not implement all these options.

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. The test mode leaves a zero length file on the receiving system.

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.