Read the chat script from the chat file. The use of this option is mutually exclusive with the chat script parameters. The user must have read access to the file. Multiple lines are permitted in the file. Space or horizontal tab characters should be used to separate the strings.
Set the timeout for the expected string to be received. If the string is not received within the time limit then the reply string is not sent. An alternate reply may be sent or the script will fail if there is no alternate reply string. A failed script will cause the chat program to terminate with a non-zero error code.
Set the file for output of the report strings. If you use the keyword REPORT, the resulting strings are written to this file. If this option is not used and you still use REPORT keywords, the stderr file is used for the report strings.
Start with the echo option turned on. Echoing may also be turned on or off at specific points in the chat script by using the ECHO keyword. When echoing is enabled, all output from the modem is echoed to stderr.
Enables environment variable substituion within chat scripts using the standard $xxx syntax.
Request that the chat script be executed in a verbose mode. The chat program 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 the SYSLOG; the logging method may be altered with the -S and -s flags.
Request that the chat script be executed in a stderr verbose mode. The chat program 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 chat or pppd program.
Use stderr. All log messages from '-v' and all error messages will be sent to stderr.
Do not use the SYSLOG. By default, error messages are sent to the SYSLOG. The use of -S will prevent both log messages from '-v' and error messages from being sent to the SYSLOG.
Pass in an arbitary string, usually a phone number, that will be substituted for the T substitution metacharacter in a send string.
Pass in a second string, usually a phone number, that will be substituted for the U substitution metacharacter in a send string. This is useful when dialing an ISDN terminal adapter that requires two numbers.
The chat script defines the communications.
A script consists of one or more
ogin:-BREAK-ogin: ppp ssword: hello2u2
This line indicates that the chat program should expect the string ''
Once it received the login prompt the chat program will send the string ppp and then expect the prompt ''
A carriage return is normally sent following the reply string. It is not expected in the
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
A very simple script might look like this:
ogin: ppp ssword: hello2u2
In other words, expect ....ogin:, send ppp, expect ...ssword:, send hello2u2.
In actual practice, simple scripts are rare. At the vary least, you should include sub-expect sequences should the original string not be received. For example, consider the following script:
ogin:--ogin: ppp ssword: hello2u2
Comments can be embedded in the chat script. A comment is a line which starts with the # (hash) character in column 1. Such comment lines are just ignored by the chat program. 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:
Many modems will report the status of the call as a string. These strings may be CONNECTED or NO CARRIER or BUSY. It is often desirable to terminate the script should the modem fail to connect to the remote. The difficulty is that a script would not know exactly which modem string it may receive. On one attempt, it may receive BUSY while the next time it may receive NO CARRIER.
These ABORT'' sequence. It is written in the script as in the following example:
ABORT BUSY ABORT 'NO CARRIER' '' ATZ OK ATDT5551212 CONNECT
The SAY directive allows the script to send strings to the user at the terminal via standard error. If chat is being run by pppd, 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.
SAY strings must be enclosed in single or double quotes. If carriage return and line feed are needed in the string to be output, you must explicitely add them to your string.
The SAY strings 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 ATDT5551212 TIMEOUT 120 SAY CONNECT SAY ogin: account ssword: pass $ SAY etc ...''
This sequence will only present the SAY strings to the user and all the details of the script will remain hidden. For example, if the above script works, the user will see:
A report string is similar to the ABORT string. 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 chat user. 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 to no change the completion code of the program.
These REPORT'' sequence. It is written in the script as in the following example:
REPORT CONNECT ABORT BUSY ATDT5551212 CONNECT ogin: account
The echo options controls whether the output from the modem is echoed to stderr. This option may be set with the -e option, but it can also be controlled by the ECHO keyword. The ECHO ON enables echoing, and ECHO OFF disables 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' OKrn ATD1234567 rn c ECHO ON CONNECT c ogin: account
The HANGUP options control whether a modem hangup should be considered as an error or not. This option is useful in scripts for dialling systems which will hang up and call your system back. The HANGUP options can be ON or OFF. When HANGUP is set OFF and the modem hangs up (e.g., after the first stage of logging in to a callback system), chat will 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 ON directive to reinstall normal hang up signal behavior. Here is an (simple) example script:
The initial timeout value is 45 seconds. This may be changed using the -t parameter.
To change the timeout value for the next expect string, the following example may be used:
ATZ OK ATDT5551212 CONNECT TIMEOUT 10 ogin:--ogin: TIMEOUT 5 assword: hello2u2
This will change the timeout to 10 seconds when it expects the login: prompt. The timeout is then changed to 5 seconds when it looks for the password prompt.
The expect and reply strings may contain escape sequences. All of the sequences are legal in the reply string. Many are legal in the expect. Those which are not valid in the expect sequence are so indicated.
Expects or sends a null string. If you send a null string then it will still send the return character. This sequence may either be a pair of apostrophe or quote characters.
represents a backspace character.
Suppresses the newline at the end of the reply string. This is the only method to send a string without a trailing return character. It must be at the end of the send string. For example, the sequence helloc will simply send the characters h, e, l, l, o. (not valid in expect.)
Delay for one second. The program uses sleep(1) which will delay to a maximum of one second. (not valid in expect.)
Insert a BREAK (not valid in expect.)
Send a newline or linefeed character.
Send a null character. The same sequence may be represented by 0. (not valid in expect.)
Pause for a fraction of a second. The delay is 1/10th of a second. (not valid in expect.)
Suppress writing the string to the SYSLOG file. The string ?????? is written to the log in its place. (not valid in expect.)
Send or expect a carriage return.
Represents a space character in the string. This may be used when it is not desirable to quote the strings which contains spaces. The sequence 'HI TIM' and HIsTIM are the same.
Send or expect a tab character.
Send the phone number string as specified with the -T option (not valid in expect.)
Send the phone number 2 string as specified with the -U option (not valid in expect.)
Send or expect a backslash character.
Collapse the octal digits (ddd) into a single ASCII character and send that character. (some characters are not valid in expect.)
The chat program will terminate with the following completion codes.
The normal termination of the program. This indicates that the script was executed without error to the normal conclusion.
One or more of the parameters are invalid or an expect string was too large for the internal buffers. This indicates that the program as not properly executed.
An error occurred during the execution of the program. This may be due to a read or write operation failing for some reason or chat receiving a signal such as SIGINT.
A timeout event occurred when there was an expect string without having a ''
The first string marked as an ABORT condition occurred.
The second string marked as an ABORT condition occurred.
The third string marked as an ABORT condition occurred.
The fourth string marked as an ABORT condition occurred.
The other termination codes are also strings marked as an ABORT condition.
Additional information about chat scripts may be found with UUCP documentation. The chat script was taken from the ideas proposed by the scripts used by the uucico program.