|CHAT(8)||System Manager's Manual||CHAT(8)|
chatprogram defines a conversational exchange between the computer and the modem. Its primary purpose is to establish a connection between the Point-to-Point Protocol Daemon (pppd(8)) and the remote's pppd process.
ECHOkeyword. When echoing is enabled, all output from the modem is echoed to stderr.
REPORT, the resulting strings are written to this file. If this option is not used and you still use
REPORTkeywords, the stderr file is used for the report strings.
-Swill prevent both log messages from
-vand error messages from being logged via syslog(3).
-vand all error messages will be sent to stderr.
chatprogram to terminate with a non-zero error code.
chatprogram will then log all text received from the modem and the output strings sent to the modem to the stderr device. This device is usually the local console at the station running the
chator pppd(8) program.
chatprogram will then log the execution state of the chat script as well as all text received from the modem and the output strings sent to the modem. The default is to log through syslog(3) with level “info”, though this may be altered with the
-foption, then the script is included as parameters to the
ogin:-BREAK-ogin: ppp ssword: hello2u2
chatprogram should expect the string “ogin:”. If it fails to receive a login prompt within the time interval allotted, it is to send a break sequence to the remote and then expect the string “ogin:”. If the first “ogin:” is received then the break sequence is not generated. Once it receives the login prompt, the
chatprogram will send the string ppp and then expect the prompt “ssword:”. When it receives the prompt for the password, it will send the password hello2u2. A carriage return is normally sent following the reply string. It is not expected in the “expect” string unless it is specifically requested by using the \r character sequence. The expect sequence should contain only what is needed to identify the string. Since it is normally stored on a disk file, it should not contain variable information. It is generally not acceptable to look for time strings, network identification strings, or other variable pieces of data as an expect string. To help correct for characters which may be corrupted during the initial sequence, look for the string “ogin:” rather than “login:”. It is possible that the leading “l” character may be received in error and you may never find the string even though it was sent by the system. For this reason, scripts look for “ogin:” rather than “login:” and “ssword:” rather than “password:”. A very simple script might look like this:
ogin: ppp ssword: hello2u2
ogin:--ogin: ppp ssword: hello2u2
chatprogram. If a ‘#’ character is to be expected as the first character of the expect sequence, you should quote the expect string. If you want to wait for a prompt that starts with a ‘#’ (hash) character, you would have to write something like this:
# Now wait for the prompt and send logout string ´# ' logout
ABORTsequence. It is written in the script as in the following example:
ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
ABORTstrings are kept in an array of a pre-determined size (at compilation time);
CLR_ABORTwill reclaim the space for cleared entries so that new strings can use that space.
SAYdirective allows the script to send strings to the user at the terminal via standard error. If
chatis being run by pppd(8), and pppd is running as a daemon (detached from its controlling terminal), standard error will normally be redirected to the file /etc/ppp/connect-errors.
SAYstrings must be enclosed in single or double quotes. If carriage return and line feed are needed in the string to be output, you must explicitly add them to your string. The
SAYstrings could be used to give progress messages in sections of the script where you want to have 'ECHO OFF' but still let the user know what is happening. An example is:
ABORT BUSY ECHO OFF SAY "Dialling your ISP...\n" ´' ATDT5551212 TIMEOUT 120 SAY "Waiting up to 2 minutes for connection ... " CONNECT '' SAY "\nConnected, now logging in ...\n" ogin: account ssword: pass $ SAY "Logged in OK ...\n" etc ...
SAYstrings to the user and all the details of the script will remain hidden. For example, if the above script works, the user will see:
Dialling your ISP... Waiting up to 2 minutes for connection ... Connected, now logging in ... Logged in OK ...
ABORTstring. The difference is that the strings, and all characters to the next control character such as a carriage return, are written to the report file. The report strings may be used to isolate the transmission rate of the modem's connect string and return the value to the
chatuser. The analysis of the report string logic occurs in conjunction with the other string processing such as looking for the expect string. The use of the same string for a report and abort sequence is probably not very useful; however, it is possible. The report strings do not change the completion code of the program. These “report” strings may be specified in the script using the
REPORTsequence. It is written in the script as in the following example:
REPORT CONNECT ABORT BUSY '' ATDT5551212 CONNECT '' ogin: account
REPORTstrings are kept in an array of a pre-determined size (at compilation time);
CLR_REPORTwill reclaim the space for cleared entries so that new strings can use that space.
-eoption, but it can also be controlled by the
ECHOkeyword. The “expect-send” pair
ECHO ONenables echoing, and
ECHO OFFdisables it. With this keyword you can select which parts of the conversation should be visible. For instance, with the following script:
ABORT 'BUSY' ABORT 'NO CARRIER' '' ATZ OK\r\n ATD1234567 \r\n \c ECHO ON CONNECT \c ogin: account
HANGUPoptions control whether a modem hangup should be considered as an error or not. This option is useful in scripts for dialing systems which will hang up and call your system back. The
HANGUPoptions can be
OFFand the modem hangs up (e.g., after the first stage of logging in to a callback system),
chatwill continue running the script (e.g., waiting for the incoming call and second-stage login prompt). As soon as the incoming call is connected, you should use the
HANGUP ONdirective to reinstall normal hangup signal behavior. Here is an example script:
ABORT 'BUSY' '' ATZ OK\r\n ATD1234567 \r\n \c CONNECT \c ´Callback login:' call_back_ID HANGUP OFF ABORT "Bad Login" ´Callback Password:' Call_back_password TIMEOUT 120 CONNECT \c HANGUP ON ABORT "NO CARRIER" ogin:--BREAK--ogin: real_account etc ...
-tparameter. The following example illustrates how to change the timeout value for the next expect string:
ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2
EOTindicates that the
chatprogram should send an EOT character to the remote. This is normally the End-of-file character sequence. A return character is not sent following the EOT. The EOT sequence may be embedded into the send string using the sequence ^D.
BREAKwill cause a break condition to be sent. The break is a special signal on the transmitter. The normal processing on the receiver is to change the transmission rate. It may be used to cycle through the available transmission rates on the remote until you are able to receive a valid login prompt. The break sequence may be embedded into the send string using the \K sequence.
BREAK. (Not valid in expect.)
chatprogram will terminate with the following completion codes:
chatreceiving a signal such as
chatprogram is in the public domain. This is not the GNU public license. If it breaks then you get to keep both pieces.
|July 25, 2011||OpenBSD-current|