% PICOCOM(1)

---
header: User Commands
---

# NAME

picocom - minimal dumb-terminal emulation program


# SYNOPSIS

**picocom** [ _options_ ] _device_


# DESCRIPTION

As its name suggests, **picocom(1)** is a minimal dumb-terminal
emulation program. It is, in principle, very much like **minicom(1)**,
only it's "pico" instead of "mini"! It was designed to serve as a
simple, manual, modem configuration, testing, and debugging tool. It
has also served (quite well) as a low-tech serial communications
program to allow access to all types of devices that provide serial
consoles. It could also prove useful in many other similar tasks.

In effect, picocom is not an "emulator" per-se. It is a simple program
that opens, configures, manages a serial port (tty device) and its
settings, and connects to it the terminal emulator you are, most
likely, already using (the terminal window application, xterm, rxvt,
system console, etc).

When picocom starts it opens the tty (serial port) given as its
non-option argument (or the *last* non-option argument, if multiple
are given). Unless the **--noinit** option is given, it configures the
port to the settings specified by the option-arguments (or to some
default settings), and sets it to "raw" mode. If **--noinit** is
given, the initialization and configuration is skipped; the port is
just opened. Following this, if standard input is a tty, picocom sets
the tty to raw mode. Then it goes in a loop where it listens for input
from stdin, or from the serial port. Input from the serial port is
copied to the standard output while input from the standard input is
copied to the serial port. Picocom also scans its input stream for a
user-specified control character, called the _escape character_ (being
by default **C-a**). If the escape character is seen, then instead of
sending it to the serial-device, the program enters "command mode" and
waits for the next character (which is called the "function
character"). Depending on the value of the function character, picocom
performs one of the operations described in the **[COMMANDS]** section
below.


# COMMANDS

Commands are given to picocom by first keying the *espace character*
which by default is **C-a** (see **[OPTIONS]** below for how to change
it), and then keying one of the function (command) characters shown
here.

*escape character*

:   Send the escape character to the serial port and return to
    "transparent" mode. This means that if the escape character
    (**C-a**, by default) is typed twice, the program sends the escape
    character to the serial port, and remains in transparent mode.

**C-x**

:   Exit the program. If the **--noreset** option is *not* given, then
    the serial port is reset to its original settings before exiting,
    and the modem control lines (typically DTR and RTS) are cleared
    (lowered) signaling a modem hangup. If **--noreset** is given (and
    **--hangup** is not), then the serial port settings are not reset,
    and the modem control lines remain unaffected. If both
    **--noreset** and **--hangup** are given, then the serial port
    settings are not reset, but the modem-control lines *are* cleared.

**C-q**

:   Quit the program *without* resetting the serial port to its
    original settings. Terminating with the Quit command, picocom
    behaves *exactly* as if the **--noreset** option was given. The
    serial port is *not* reset to its original settings, and the modem
    control lines remain unaffected or are cleared, subject to the
    **--hangup** option.

**C-p**

:   Pulse the DTR line. Lower it for 1 sec, and then raise it again.

**C-t**

:   Toggle the DTR line. If DTR is up, then lower it. If it is down,
    then raise it. May not be supported on some systems.

**C-g**

:   Toggle the RTS line. If RTS is up, then lower it. If it is down,
    then raise it. Not supported if the flow control mode is RTS/CTS.
    May not be supported on some systems.

**C-backslash**

:   Generate a break sequence on the serial line. A break sequence is
    usually generated by marking (driving to logical one) the serial
    Tx line for an amount of time corresponding to several character
    durations.

**C-b**

:   Set baudrate. Prompts you to enter a baudrate numerically (in bps)
    and configures the serial port accordingly.

**C-u**

:   Baud up. Increase the baud-rate. The list of baud-rates
    stepped-through by this command is: 50, 75, 110, 134, 150, 200,
    300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200.  If
    `HIGH_BAUD` support is compiled-in, then the following baud-rates
    are also added to the list: 230400, 460800, 500000, 576000,
    921600, 1000000, 1152000, 1500000, 2000000, 2500000, 3000000,
    3500000, 4000000. Depending on you system, any of the higher baud
    rates may be missing.

**C-d**

:   Baud down. Decrease the baud-rate. The list of baud-rates
    stepped-through by this command is the same as for the "baud-up"
    command.

**C-f**

:   Cycle through flow-control settings (RTS/CTS, XON/XOFF, none).

**C-y**

:   Cycle through parity settings (even, odd, none).

**C-i**

:   Cycle through databits-number settings (5, 6, 7, 8).

**C-j**

:   Cycle through stopbits-number settings (1, 2).

**C-c**

:   Toggle local-echo mode.

**C-w**

:   Write hex. Picocom prompts the user for a string of hexadecimal
    values. Values can be entered with or without delimiters
    (separators). The hexadecimal values are translated to binary and
    sent to the port, exactly as if input at the terminal (i.e. the
    **--omap**, **--echo** and **--emap** options are
    observed). Example: The following sends the characters "ABCD" to
    the port.

        C-a C-w
        *** hex: 41 4243:44
        *** wrote 4 bytes ***

**C-s**

:   Send (upload) a file. See **[SENDING AND RECEIVING FILES]**
    below.

**C-r**

:   Receive (download) a file. See **[SENDING AND RECEIVING FILES]**
    below.

**C-v**

:   Show program options (like baud rate, data bits, etc) as well as
    the actual serial port settings. Only the options and port
    settings that can be modified online (through commands) are shown,
    not those that can only be set at the command-line. See
    **[DISPLAY OF OPTIONS AND PORT SETTINGS]** for details.

**C-h** or **C-k**

:   Show help, or show keys. Prints a short description of all
    available function (command) keys.

After performing one of the above operations, the program leaves the
command mode and enters transparent mode. Example: To increase the
baud-rate by two steps, you have to type:

> **C-a**, **C-u**, **C-a**, **C-u**

assuming of-course that **C-a** is the escape character.


# OPTIONS

Picocom accepts the following command-line options.

**--baud** | **-b**

:   Defines the baud-rate to set the serial-port (terminal) to.

**--flow** | **-f**

:   Defines the flow-control mode to set the serial-port to. Must be
    one of: **x** for xon/xoff (software) mode, **h** for hardware
    flow control (RTS/CTS), **n** for no flow control. (Default:
    **n**)

**--parity** | **-y**

:   Defines the parity mode to set the serial-port to.  Must be one
    of: **o** for odd parity mode, **e** for even parity mode, **n**
    for no parity mode. (Default: **n**)

**--databits** | **-d**

:   Defines the number of data bits in every character. Must be one
    of: **5**, **6**, **7**, **8**. (Default: **8**)

**--stopbits** | **-p**

:   Defines the number of stop bits in every character. Must be one
    of: **1**, or **2**. (Default: **1**)

**--escape** | **-e**

:   Defines the character that will make picocom enter command-mode
    (see description above). If **x** is given, then **C-x** will make
    picocom enter command mode. See also the **--no-escape**
    option. (Default: **a**)

**--no-escape** | **-n**

:   Disables the escape character. Picocom will never enter
    command-mode if this option is given. To exit picocom, in this
    case, you must either close its standard input, or send it the
    TERM or INT signal. (Default: Disabled).

**--echo** | **-c**

:   Enable local echo. Every character being read from the terminal
    (standard input) is echoed to the terminal (standard output)
    subject to the echo-mapping configuration (see **--emap**
    option). (Default: Disabled)

**--noinit** | **-i**

:   If given, picocom will not initialize, configure, or otherwise
    mess with the serial port at start-up. It will just open it. This
    is useful, for example, for connecting picocom to
    already-connected modems, or already configured ports without
    terminating the connection, or altering their settings. If
    required, serial port parameters can then be adjusted at run-time
    by commands. See also the **--noreset** and **--hangup**
    options. (Default: Disabled)

**--noreset** | **-r**

:   If given, picocom will not reset the serial port when exiting. It
    will just close the respective file descriptor and do nothing
    more. The serial port settings will *not* be restored to their
    original values and, unless the **--hangup** option is also given,
    the modem-control lines will *not* be affected. This is useful,
    for example, for leaving modems connected when exiting
    picocom. Regardless whether the **--noreset** option is given, the
    user can exit picocom using the "Quit" command (instead of
    "Exit"), which makes picocom behave *exactly* as if **--noreset**
    was given. See also the **--hangup** option. (Default: Disabled)

    NOTICE: Picocom clears the modem control lines on exit by setting
    the *HUPCL* control bit of the respective port. Picocom always
    sets HUPCL according to the **--noreset** and **--hangup**
    options. If **--noreset** is given and **--hangup** is not, then
    HUPCL for the port is cleared and will remain so after exiting
    picocom. If **--noreset** is *not* given, or if both **--noreset**
    and **--hangup** are given, then HUPCL is set for the port and
    will remain so after exiting picocom. This is true, regardless of
    the way picocom terminates (command, read zero-bytes from standard
    input, killed by signal, fatal error, etc), and regardless of the
    **--noinit** option.

**--hangup** | **-u**

:   If given together with **--noreset**, picocom will not reset the
    serial port to it's original settings on exit, but it *will* clear
    the modem control lines (typically DTR and RTS) to signal a modem
    hangup. Without the **--noreset** option (explicitly given, or
    implied by exiting with the "Quit" command) **--hangup** has no
    effect (without **--noreset** picocom always clears the modem
    control lines on exit, anyway).

**--nolock** | **-l**

:   If given, picocom will _not_ attempt to lock the serial port
    before opening it. Normally, depending on how it's compiled,
    picocom attempts to get a UUCP-style lock-file
    (e.g. '/var/lock/LCK..ttyS0') before opening the port, or attempts
    to lock the port device-node using **flock(2)**. Failing to do so,
    results in the program exiting after emitting an error-message. It
    is possible that your picocom binary is compiled without support
    for locking. In this case the **--nolock** option is accepted, but
    has no effect. (Default: Disabled)

**--send-cmd** | **-s**

:   Specifies the external program (and any arguments to it) that will
    be used for transmitting files. If the argument to **--send-cmd**
    is the empty string (''), the send-file command is disabled. See
    **[SENDING AND RECEIVING FILES]**. (Default: **sz -vv**)

**--receive-cmd** | **-v**

:   Specifies the external program (and any arguments to it) that will
    be used for receiving files. If the argument to **--receive-cmd**
    is the empty string (''), the receive-file command is
    disabled. See **[SENDING AND RECEIVING FILES]**. (Default: **rz
    -vv**)

**--imap**

:   Specifies the input character map (i.e. special characters to be
    replaced when read from the serial port). See
    **[INPUT, OUTPUT, AND ECHO MAPPING]**. (Default: Empty)

**--omap**

:   Specifies the output character map (i.e. special characters to be
    replaced before being written to serial port). See
    **[INPUT, OUTPUT, AND ECHO MAPPING]**. (Default: Empty)

**--emap**

:   Specifies the local-echo character map (i.e. special characters to
    be replaced before being echoed-back to the terminal, if
    local-echo is enabled). See
    **[INPUT, OUTPUT, AND ECHO MAPPING]**. (Defaul: **delbs,crcrlf**)

**--logfile** | **-g**

:   Use specified file for logging (recording) serial input, and
    possibly serial output. If the file exists, it is appended to.
    Every character read from the serial port is written to the
    specified file (before input mapping is performed). If local-echo
    mode is is enabled (see **--echo** option and **C-c** command),
    then every character written to the serial port (after output
    mapping is performed) is also logged to the same file. (Default:
    no logging)

**--initstring** | **-t**

:   Send the provided string after opening and configuring the serial
    port. The init string is sent exactly as if it was input at the
    terminal. Sending the init string, picocom observes the **--omap**
    output mapping, the **--echo** local-echo setting, and the
    **--emap** local-echo mapping. This feature is useful, for
    example, if the serial device needs some special magic strings to
    start responding. Use **echo(1)** or **xxd(1)** to generate
    special characters like a CR or binary data. Example:

        picocom -t "$(echo -ne 'AAATZ\r\n')" /dev/ttyS0

    Note, that the init string is not sent if **--noinit** is
    given. (Default: empty).

**--lower-rts**

:   Lower the RTS modem control signal after opening the serial port.
    Only supported when flow-control mode is not set to RTS/CTS,
    ignored otherwise. Only supported on some systems.

    If neither **--lower-rts** nor **--raise-rts** are given, the
    state of the RTS signal, after opening and configuring the port, is
    system dependent. On most systems the signal is raised.

**--raise-rts**

:   Raise the RTS modem control signal after opening the serial port.
    Only supported when flow-control mode is not set to RTS/CTS,
    ignored otherwise. Only supported on some systems.

    If neither **--raise-rts** nor **--lower-rts** are given, the
    state of the RTS signal, after opening and configuring the port, is
    system dependent. On most systems the signal is raised.

**--lower-dtr**

:   Lower the DTR control signal after opening the serial port. Only
    supported on some systems.

    If neither **--lower-dtr** nor **--raise-dtr** are given, the
    state of the DTR signal, after opening and configuring the port,
    is system dependent. On most systems the signal is raised.

**--raise-dtr**

:   Raise the DTR control signal after opening the serial port. Only
    supported on some systems.

    If neither **--raise-dtr** nor **--lower-dtr** are given, the
    state of the DTR signal, after opening and configuring the port,
    is system dependent. On most systems the signal is raised.


**--exit-aftrer** | **-x**

:   Exit picocom if it remains idle for the specified time (in
    milliseconds). Picocom is considered idle if: Nothing is read
    (received) from the serial port, AND there is nothing to write
    (send) to the serial port, AND nothing is read from the standard
    input (terminal). If **--exit-after** is set to zero, then picocom
    exits after opening and configuring the serial port, after sending
    the init string (if any, see option **--initstring**) and
    immediately when it becomes idle. When exiting after being idle,
    picocom drains the O/S serial port output buffer (i.e. waits for
    data already written to the port to be transmitted) and observes
    the **--noreset** and **--hangup** options as usual. (Default: not
    set).

    NOTICE: If **--exit-after** is set, reading zero bytes from the
    standard input (which usually means that whatever was connected
    there has been closed), will *not* cause picocom to exit. Instead,
    picocom will keep running, *without* reading from stdin, and will
    exit only when it becomes idle for the specified time, or if it is
    killed by a signal. If **--exit-after** is *not* set, then reading
    zero bytes from the standard input causes picocom to exit, after
    the contents of its output queue have been transmitted.

**--exit** | **-X**

:    Exit picocom immediately after opening and configuring the serial
     port. Do *not* read *anything* from the standard input or from
     the serial port. When exiting the **--noreset** and **--hangup**
     options are observed as usual. With **--exit** and **--noreset**
     (and possibly **--hangup**) picocom can be used as a very crude
     replacement of **stty(1)**. If an init string is also given (see
     **--initstring** option), picocom exits imediatelly after sending
     (writing) the init string to the serial port and draining the O/S
     serial port output buffer (i.e. waiting for data written to the
     port to be transmitted). Again, nothing is read from the standard
     input, or from the serial port. The **--exit** option, overrides
     the **--exit-after** option. (Default: Disabled)

**--quiet** | **-q**

:   Forces picocom to be quiet. Suppresses the output of the initial
    status and options information, as well as any other information or
    messages not explicitly requested by the user. Responses to user
    commands and any error or warning messages are still printed.

**--help** | **-h**

:   Print a short help message describing the command-line
    options. Picocom's version, compile-time options, and enabled
    features are also shown.


# DISPLAY OF OPTIONS AND PORT SETTINGS

The "show program options" command (**C-v**), as well as the commands
that change program options (**C-b**, **C-u**, **C-d**, **C-f**, etc)
print messages showing the current values (or the new values, if they
were changed) for the respective options. If picocom determines that
an actual serial-port setting differs from the current value of the
respective option (for whatever reason), then the value of the option
is shown followed by the value of the actual serial-port setting in
parenthesis. Example:

    *** baud: 115200 (9600)

This means that a baud rate of 115200bps has been selected (from the
command line, or using commands that change the baudrate) but the
serial-port is actually operating at 9600bps (the driver may not
support the higher setting, and has silently replaced it with a safe
default, or the setting may have been changed from outside
picocom). If the option and the corresponding serial-port setting are
the same, only a single value is shown. Example:

    *** baud: 9600

This behavior was introduced in picocom 2.0. Older releases displayed
only the option values, not the actual serial-port settings
corresponding to them.

On startup, after the serial port is opened and configured (and
assuming that neither the **--noinit**, nor the **--quiet** command
line options have been given), the port settings are silently
checked. If any mismatch is detected between the requested and the
actual port settings, a warning message is displayed. You may then use
the **[C-v]** command to determine the exact mismatch or mismatches.

# SENDING AND RECEIVING FILES

Picocom can send and receive files over the serial port using external
programs that implement the respective protocols. In Linux typical
programs for this purpose are:

- **rx(1)** - receive using the X-MODEM protocol
- **rb(1)** - receive using the Y-MODEM protocol
- **rz(1)** - receive using the Z-MODEM protocol
- **sx(1)** - send using the X-MODEM protocol
- **sb(1)** -  send using the Y-MODEM protocol
- **sz(1)** - send using the Z-MODEM protocol
- **ascii-xfr(1)** - receive or transmit ASCII files

The name of, and the command-line options to, the program to be used
for transmitting files are given by the **--send-cmd**
option. Similarly the program to receive files, and its arguments, are
given by the **--receive-cmd** option. For example, in order to start
a picocom session that uses **sz(1)** to transmit files, and **rz(1)**
to receive files, you have to say something like this:

    picocom --send-cmd "sz -vv" --receive-cmd "rz -vv" ...

If the argument to the **-send-cmd** option, or the argument to the
**--receive-cmd** option is the empty string, then the respective
command is disabled. For example, in order to disable both the "send"
and the "receive" commands you can invoke picocom like this:

    picocom --send-cmd '' --receive-cmd '' ...

A picocom session with both, the send- and the receive-file commands
disabled does not **fork(2)** and does not run any external programs.

During the picocom session, if you key the "send" or "receive"
commands (e.g. by pressing **C-a**, **C-s**, or **C-a**, **C-r**) you
will be prompted for a filename. At this prompt you can enter one or
more file-names, and any additional arguments to the transmission or
reception program. Command-line editing and rudimentary pathname
completion are available at this prompt, if you have compiled picocom
with support for the linenoise library. Pressing **C-c** at this
prompt will cancel the file transfer command and return to normal
picocom operation. After entering a filename (and / or additional
transmission or reception program arguments) and assuming you have not
canceled the operation by pressing **C-c**, picocom will start the
external program as specified by the **--send-cmd**, or
**--receive-cmd** option, and with any filenames and additional
arguments you may have supplied. The standard input and output of the
external program will be connected to the serial port. The standard
error of the external program will be connected to the terminal
which---while the program is running---will revert to canonical
mode. Pressing **C-c** while the external program is running will
prematurely terminate it (assuming that the program itself does not
ignore SIGINT), and return control to picocom. Pressing **C-c** at any
other time, has no special effect; the character is normally passed to
the serial port.


# INPUT, OUTPUT, AND ECHO MAPPING

Using the **--imap**, **--omap**, and **--emap** options you can make
picocom map (translate, replace) certain special characters after being
read from the serial port (with **--imap**), before being written to
the serial port (with **--omap**), and before being locally echoed to
the terminal (standard output) if local echo is enabled (with
**--emap**). These mapping options take, each, a single argument which
is a comma-separated list of one or more of the following identifiers:

- **crlf** (map CR to LF),
- **crcrlf** (map CR to CR + LF),
- **igncr** (ignore CR),
- **lfcr** (map LF to CR),
- **lfcrlf** (map LF to CR + LF),
- **ignlf** (ignore LF),
- **bsdel** (map BS to DEL),
- **delbs** (map DEL to BS)
- **spchex** (map special chars (< 0x20 || 0x7f), excl. CR, LF, and
TAB to hex)
- **tabhex** (map TAB to hex)
- **crhex** (map CR to hex)
- **lfhex** (map LF to hex)
- **8bithex** (map chars with 8th-bit set to hex)
- **nrmhex** (map normal ascii chars (0x20 <= c < 0x7f) to hex)

The "to hex" mappings (**???hex**) replace the respective characters
with their hexadecimal representation (in square brackets), like this:

    CR --> [0d]

If more than one mappings are provided that apply to the same
character, then only the first mapping, in the order listed above, is
applied.

For example the command:

    picocom --omap crlf,delbs --imap ignlf,bsdel --emap crcrlf ...

will:

- Replace every CR (carriage return, 0x0d) character with LF (line
  feed, 0x0a) and every DEL (delete, 0x7f) character with BS
  (backspace, 0x08) before writing it to the serial port.

- Ignore (not write to the terminal) every LF character read from the
  serial port, and replace every BS character read from the serial
  port with DEL.

- Replace every CR character with CR and LF when echoing to the
  terminal (if local-echo is enabled).


# EXITING PICOCOM

This section summarizes the conditions in which picocom terminates its
operation and what happens in each such condition:

- The exit command is seen in the standard input. That is, the escape
  character is seen (default **C-a**), followed by the exit command
  character (default **C-x**). In this case: The contents of the
  output queue (data read from the standard input, but not yet written
  to the port) as well as the contents of the O/S serial port output
  buffer (data already written to the port, but not yet transmitted)
  are discarded (flushed). Then the serial port is reset to it's
  original settings, and the modem-control lines are cleared signaling
  a modem reset, subject to the **--noreset** and the **--hangup**
  options. After that picocom exits with a success status.

- The quit command is seen in the standard input. That is, the escape
  character is seen (default **C-a**), followed by the quit command
  character (default **C-q**). The behavior in this case is similar to
  that of the exit command, with one difference: Picocom behaves as if
  the **--noreset** option is given (regardless if it actually is, or
  not).

- The **--exit** option is given. See the documentation of this option
  for a description of what exactly happens in this case. Picocom
  exits with a success exit status.

- The **--exit-after** option is given. See the documentation of this
  option for a description of what exactly happens in this
  case. Picocom exits with a success exit status.

- Zero bytes are read from the standard input. This usually means that
  whatever was connected to picocom's standard input has been closed
  or, if a file was connected, then picocom has read up to the end of
  the file. In this case, if the **--exit-after** option is *not*
  given, picocom stops reading from the standard input, and keeps
  operating normally (i.e. writing to, and reading from, the serial
  port) until its output queue empties. When this happens, picocom
  waits for the O/S serial port output buffer to drain and then
  (subject to the **--noreset** and **--hangup** options) resets the
  serial port to it's initial settings, clears the modem-control
  lines, and exits. If the **--exit-after** option is given then,
  again, picocom stops reading from the standard input and continues
  operating normally but, in this case, it does so until it becomes
  idle for the specified amount of time, before exiting. Picocom exits
  with a success exit status.

- Picocom is killed by the TERM or INT signal, or an unrecoverable
  error occurs. In this case picocom behaves as if it had received the
  exit command, that is: The contents of the output queue and the
  contents of the O/S serial port output buffer are discarded
  (flushed). Then, subject to the **--noreset** and **--hangup**
  options, the serial port is reset to its original settings, the
  modem control lines are cleared, and picocom exits with a failure
  status.


# AUTHOR

Written by Nick Patavalis <npat@efault.net>


# AVAILABILITY

Download the latest release from:
<https://github.com/npat-efault/picocom/releases>


# COPYRIGHT

Copyright (c) 2003-2018 Nick Patavalis

This file is part of Picocom.

Picocom is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.

Picocom is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA