REX

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
REX RUN
REX COPY
REX COPY−FROM
REX LOGIN
REX LIST
REX EDIT
CONFIG ARRAY
REX DATABASE
NOTES
FILES
ENVIRONMENT
RETURN VALUE
EXAMPLE
AUTHORS
BUG REPORTS
COPYRIGHT

NAME

rex − remote execution utility

SYNOPSIS

rex [−NVdlnvh] [−c FILE] [−−config=FILE] [−−noop] [−−no−init−file] [−−no−rc−file] [−−no−resolve] [−−verbose] [−−version] [−−help] COMMAND
[ARG...]

DESCRIPTION

Rex runs a supplied command or shell script on several hosts in succession or in parallel. It can also be used to copy a file or files to several hosts.

The two main COMMANDs are run, which runs the specified command on multiple hosts, and copy, or cp, which copies files to them.

For both commands, there are two ways to select hosts to operate upon.

The first way is the −H (−−host) option. Its argument is either a single hostname or IP, or a comma-separated list of hostnames or IP addresses. The option adds these hosts to the list. Multiple options can be specified.

The −H option exists mainly as a way of quickly running a job of several hosts at once. If you have a set of hosts which you often work with, it’s best to use a hostgroup.

A hostgroup defines a list of hosts and, optionally, a set of rex settings to use when running commands on them. Each hostgroup is identified by its name and is defined in a separate disk file. See the subsection Hostgroups, for a detailed discussion of how to define a hostgroup.

Once defined, the option −g (−−group) can be used to run a command on each host in the group. The argument to the option is the name of the group. Thus, e.g.

rex run −gNAME COMMAND

runs COMMAND on hosts from hostgroup NAME, and

rex copy −gNAME FILE /tmp

copies FILE to the directory /tmp on each host from this hostgroup.

The list of hosts in a hostgroup can be modified for the duration of a single rex command by using the −H and −X options. The −H (−−host) option works exactly as described above. The −i (−−ignore−hosts) option can be given to ignore the list of hosts defined in the hostgroup and operate only on those supplied with the −−host options.

The −X (−−exclude) option instructs rex to remove its argument from the list of hosts. The argument must be a domain name or IP address of the host. It need not be exactly the same name or IP as the one used in the set hosts statement in the rc file. It suffices that it resolves to the same IP as one of the hosts listed in the hostgroup.

The list of all available hostgroups can be obtained using the list command. The list is organized in two columns: group name and its short description (if available).

Login credentials
Normally, remote hosts should be configured to accept logins to the user account without password, by using shared keys. However, it is also possible to work on hosts requiring password for authentication. To do so, rex keeps the database of login credentials. The database is edited using the command

rex edit

This command starts the editor defined by the VISUAL (or, if unset, EDITOR) environment variable. Upon exit from the editor, it compares the new content with the existing one. If changed, the user is prompted whether they wish to save the changes.

The database is a dictionary of key-value pairs. A key identifies the credential (e.g. user, for username, or pass, for password). Unless prefixed with one or more qualifiers, it is valid for all servers in all hostgroups. Qualifiers limit the scope of a key to a given hostgroup or server.

In general, the syntax for a key is:

[[GROUP:][HOST]:]KEYWORD

When looking for a key, the most qualified match is preferred, so the lookup order is:

1.

GROUP:HOST:KEYWORD

2.

HOST:KEYWORD

3.

GROUP::KEYWORD

4.

KEYWORD

For example, to determine the login name for the given host, rex looks up for the keyword user. If no matching key is found and the the −u (−−user) option is given, its value is used. Otherwise, the name of the value of the environment variable USER is used.

Similarly, the password to use is determined by the following look-ups:

1.

GROUP:HOST:pass

2.

HOST:pass

3.

GROUP::pass

4.

pass

If none of these keys is found, the value of the −p (−−password) option is used. If this option is not supplied either, passwordless account is assumed.

Configuration files
Upon startup rex looks for the following files and attempts to source them:
/etc/rex/rc

System-wide configuration file.

~/.rex/rc

User-specific configuration file.

These files are not required to exist. If they do the user settings override the system-wide ones.

These files are sourced as regular TCL code. Normally, they modify the rex settings by using a st of commands provided for that purpose:
host
HOSTNAME [HOSTNAME...]

Adds the listed hostnames to the list of hosts.

ifmode { mode body [mode body...] }

Matches the current mode agains each of mode arguments. As soon as the match is found, the corresponding body is evaluated. Similarly to the switch(n) command, a dash in place of body means that the body for the next mode should also be used as the body for this one. If the next mode has a body of "−", than the body after that is used, etc.) The mode should be one of the following: run, copy−to, copy−from, login, list, and edit. If the last mode used is the word default, it will match any mode not explicitly listed before.

The ifmode pattern allows for selecting different settings depending on the running mode. For example, it is common to set the TERM environment variable to dumb for run mode. However, it is undesirable in login and edit modes, and has no effect on the remaining modes. To make sure it is set only for run mode, the following statement is normally used:

ifmode {
  run { environ TERM=dump }
}

option OPTNAME VALUE [VALUE...]

Sets or unsets an rex option. OPTNAME is the long name of the option without the leading two dashes. For example, setting

option jobs 25

has the same effect as giving the option −−jobs=25 in the command line.

Options that take no argument in the command line are treated as booleans. The VALUE of on, true, yes, or 1 sets the option, while the VALUE of off, false, no, or 0 unsets it. Thus, to set the no−resolve option, use

option no−resolve true

timeout [NUMBER]

Sets the timeout for expecting reply from the remote commands. NUMBER is the timeout value in seconds. When used without arguments, returns the current timeout value.

environ [−set] NAME=VALUE [NAME=VALUE...]

Sets environment variables.

environ -unset NAME [NAME...]

Unsets environment variables.

earlycmd [−clear] COMMAND [COMMAND...]

Defines the sequence of shell commands that will be sent as soon as the secure connection to the remote host is established, before waiting for the command line prompt. For an example of its use, see the note about ZSH, below.

shrc [−clear] COMMAND [COMMAND...]

Defines the sequence of shell commands that will be sent after receiving the first command line prompt from the remote server.

Hostgroups
A hostgroup defines a list of hosts and optionally associates a set of rex settings to use when running commands on them. Each hostgroup is identified by its name, which must comply with the same requirements as a name of a disk file. The hostgroup definition consists of one or more files located in the directory ~/.rex/hostgroup/NAME (user-specific), or /etc/rex/hostgroup/NAME (system-wide), where NAME is the name of the group. User-specific directories are given preference over the system-wide. The only mandatory file is rc. It is a TCL source, which will be loaded in a separate namespace, to avoid the possibility of inadvertent contamination of the main rex code.

Rex provides a set of basic commands for use in rc files, so normally there is no need to know rex internals in order to configure it. See the subsection Configuration files for a detailed guide.

Debugging
To see what’s going on during rex invocation. Use the −d (−−debug) option. This option is incremental, that is the more times you repeat it in the command line, the more debugging information is output. Currently, to obtain the most detailed information, it should be repeated three times (e.g. 0

Additional information is provided by the −l (−−log) option, which enables logging of the send/expect dialog to stdout.

If you wish to get even more information and are familiar with expect(1) internals, set the EXPECT_DEBUG environment variable prior to invoking rex. The value of this variable is the name of a file where to output additional information (as well as showing it on the standard error). Overall effect is equivalent to setting exp_internal in expect.

When rex encounters an error in one of its rc files, it prints the location where the error occurred and a short diagnostic message describing the nature of the error. If you wish to obtain full trace of TCL calls for such errors, use the −−tcl−trace option. Normally, this option is only useful for rex developers.

OPTIONS

−c, −−config=FILE

Read configuration from FILE.

−d, −−debug

Increase debugging level.

−l, −−log

Log everything to the standard output.

−q, −−no−init−file, −−no−rc−file

Don’t read system-wide and user configuration files.

−N, −−noop

Ignore all commands (useful for side effects).

−n, −−no−resolve

Don’t resolve IP addresses when printing hostnames.

−−tcl−trace

Produce full TCL trace if an error occurs while sourcing one of the configuration files. This option is useful mainly for developers.

−v, −−verbose

Enable additional warnings.

−V, −−version

Print program version and copyright statement.

−h, −−help

Show a terse help summary

REX RUN

rex run PROGRAM ARG [ARG...]

The rex run command runs the specified program with the arguments on the servers.

Sequential and parallel execution
By default, rex run executes the command on each host in succession. The output from the command is printed on the standard output, preceded by a header line containing the name of the remote host that produced the output, and a colon.

The −−no−host−header option disables printing of that header line. The −P (−−prefix) option further modifies the output by prefixing each line with the hostname, a greater than sign, and a space character.

When operating on a big number of hosts, the operation can be sped up by running command on several hosts at once. This parallel operation is enabled by the −jN (−−jobs=N) option. The N parameter is the number of hosts to be processed in a batch.

The −j option implies −−prefix −−no−host−header to make it clear which host produced which line. However, if the command produces multiple lines of output, they become intermixed when running in parallel. To further improve readability of the output, the −b (−−buffer−output) option is provided.

This option instructs rex to buffer output from each host in the batch and to output it only after the host closes connection. This way, output from each host appears on screen as a contiguous text.

The −b option cancels the implied −−prefix −−no−host−header settings.

Transferring data prior to execution
If the program relies on some additional files to be present, these can be transferred to each host prior to running the program. This is done using the −D (−−data−file) option. The argument to this option names the file to be copied to the target host.

To transfer multiple files, repeat the −D option for each of them.

The files supplied with the −D options will be copied to a temporary directory created in /tmp on each target host. That directory will become current working directory when invoking the PROGRAM.

The arguments to PROGRAM can refer to the files transferred via the −D option using the syntax {N}, where N is the number of the −D option occurrence (1-based). The {N} is expanded to the file name part of the argument to the corresponding −D option. For example,

rex run −D prefix.txt −D repl sed −f {2} {1} /etc/passwd

will result in running the following command in a temporary directory on each target host:

sed −f repl prefix.txt /etc/passwd

Note, that the result of expansion is always a file name, relative to the current working directory on the remote host. This means that

rex run −D /tmp/prefix.txt −D repl sed −f {2} {1} /etc/passwd

will result in exactly same command as the example above: the expansion of {1} will throw away the directory part from the file name.

Similarly, the token {} will be expanded to a space-separated list of file names passed with all −D options, in the same order they appear on the command line.

The PROGRAM itself can be an interpreted script that needs to be copied on each host for execution. The −−copy option instructs rex to create a temporary directory on the remote host, copy PROGRAM there, and then select the interpreter to run by analyzing the first line from it. If this line starts with characters #!, the rest of line is taken as the interpreter pathname and initial arguments. For example, assuming that file /libexec/foo is a shell script beginning with #!/bin/ksh, the following command:

rex run −−copy /libexec/foo /home

will first copy the file /libexec/foo to a temporary directory on the remote host, and then invoke it as

/bin/ksh foo /home

If the file does not begin with #!, the default interpreter,
/bin/sh
, will be used. The default interpreter can be changed
using the −−interpreter option, as in the following example:

rex run −−copy −−interpreter="/bin/env perl" test.pl

Scripting
When given the −s NAME option, rex run looks for the file named NAME.tcl in the library search path. The search path is scanned from left to right. The first encountered NAME.tcl file is sourced in the namespace hostproc.

The default library search path is:

~/.rex/script
/etc

If the −g GROUP (−−group=GROUP) option is given, the path is modified as follows:

~/.rex/GROUP/script
/etc/
GROUP/script
~/.rex/script
/etc

The following functions from the hostproc namespace are used by rex:
proc prologue {}

Called at the very beginning of rex invocation, after analyzing the command line options, but before parsing the remaining command line arguments.

This function can be used to initialize internal variables. It is also allowed to modify the global config array (see the section CONFIG ARRAY, below).

In the following example, prologue is used to set up the command line:

proc prologue {} {
    global config
    set config(argv) {ls −ld /home}
}

proc epilogue {}

Called after processing all hosts.

It an be used for application-specific cleanup.

proc transition {host state}

Called when the session for $host is switched to the state $state. Currently implemented states are:

INIT

The initial state. It is entered after starting ssh for that host.

PASS_SENT

Entered after receiving password prompt from the remote side and responding to it with a password.

SUDO

Entered after responding to the password prompt received in the COMMAND state. This happens only in sudo mode, when sudo asks for credentials.

SUDO2

Entered after sending a sudo rm command to remove the temporary directory.

STTY

Entered after sending the initial stty −echo command, which happens after successful authentication. The session remains in this state while sending commands from the initial command list (see the description of shrc key in CONFIG ARRAY.

COMMAND

Entered after sending the main command to the host.

LOGOUT

The very last state in the session lifetime. It is entered after sending the terminating exit command to the host.

The following implementation of the transition function uses this information to display informational message about each host being processed:

proc transition {host state} {
    if {$state == "INIT"} {
     puts −nonewline stderr "$host... "
    } elseif {$state == "LOGOUT"} {
        puts "done"
    }
}

proc getline {host line}

Invoked each time a new line of output is received from the host. The host parameter is the name of the host. The $line parameter is the line received from the host (with trailing CRLF characters).

proc finish {host refname}

The finish function is called when EOF has been received from the host. The refname parameter is a name of the variable keeping the entire text received from that host during the session. This variable exists only if rex has been instructed to buffer host output (see the −b option). If it exists, the output text is stored as a list of lines.

REX RUN OPTIONS
−b
, −−buffer−output

Output from servers is buffered and printed only when the job is finished. When running several jobs in parallel (see −−jobs option below), output lines from the concurrent jobs are printed as they arrive and can therefore appear on the screen intermixed. This option ensures that output from each server is printed as a contiguous block of text instead.

−−copy

copy PROGRAM to each host before executing

−D, −−data−file=FILE

Declares FILE as a data file which will be used by COMMAND. The file will be copied to each host prior to running the command on it.

Multiple files can be specified by repeating the −D option as many times as needed.

If −D FILE option is given, the string {} passed as one of the ARGS is replaced by FILE on the target machine. If several −D options are given, {} is replaced by their arguments. For example, the command rex run -D a -D b proc {} copies files a and b to the target machine and then runs the command proc a b.

−g, −−group=NAME

Select host group.

−h, −−help

Display short help summary.

−H, −−host=HOST[,NAME...]

Add HOST to the list. Multiple hosts can be specified as a comma-delimited list (no whitespace around commas, please).

−i, −−ignore-hosts

Ignore the list of hosts read from the hostgroup file. Operate only on hosts supplied in the command line (see the −−host option, above). This is useful to preserve the settings from the hostgroup file while executing the command on the hosts defined on the command line.

−I, −−interactive

Interactively ask for missing usernames and passwords.

−−interpreter=COMMAND

Use COMMAND as interpreter for running PROGRAM. This option implies −−copy. By default, rex determines the interpreter to use by analyzing the first line of PROGRAM.

−j, −−jobs=N

Run N jobs at once. Implies −−no−host−header −−prefix.

−−no−host−header

Don’t print hostname before output from the host.

−p, −−password=PWD

Set default password (unsafe!)

−P, −−prefix

Prefix each output line with the host name or IP.

−s, −−source=NAME

Source .rex/NAME.tcl after reading configuration files.

−−sudo

Run the command via sudo(1).

−u, −−user=NAME

Set default user name.

−w, −−confirm

Prompt and wait for confirmation before each host.

−X, −−exclude−host=HOST[,NAME...]

Remove HOST from the list. Multiple hosts can be specified as a comma-delimited list (no whitespace around commas, please).

−Z, −−zsh−quirk

Try to cope with hosts running zsh(1).

Unless special measures are taken, the output produced by zsh is heavily contaminated with special escape sequences, which makes it almost impossible to recognize command line prompts.

The −Z option forces rex to set TERM=dumb. Then, if no command line prompt is seen within the predefined interval, rex will try to disable ZLE option, set PS1 to a dollar sign followed by space and will retry scanning. This allows for properly recognizing command line prompts returned by zsh at the expense of certain slowdown. See the subsection ZSH below for more efficient ways of handling zsh.

REX COPY

rex copy [OPTIONS] FILE [FILE...] DEST

The rex copy command copies one or more FILEs to the given destination (DEST) on each remote host.

The command verb can be abbreviated to cp.

REX COPY OPTIONS
−g
, −−group=NAME

Select host group.

−h, −−help

Display short help summary.

−H, −−host=HOST[,NAME...]

Add HOST to the list. Multiple hosts can be specified as a comma-delimited list (no whitespace around commas, please).

−i, −−ignore-hosts

Ignore the list of hosts read from the hostgroup file. Operate only on hosts supplied in the command line (see the −−host option, above). This is useful to preserve the settings from the hostgroup file while executing the command on the hosts defined on the command line.

−I, −−interactive

Interactively ask for missing usernames and passwords.

−j, −−jobs=N

Run N jobs at once. Implies

−p, −−password=PWD

Set default password (unsafe!)

−P, −−prefix

Prefix each output line with the host name or IP.

−−sudo

Switch to root privileges before copying to DEST. Technically, speaking, the command

rex copy −−sudo FILE DEST

is equivalent to

rex run −D FILE cp {} DEST

−u, −−user=NAME

Set default user name.

−w, −−confirm

Prompt and wait for confirmation before each host.

−X, −−exclude−host=HOST[,NAME...]

Remove HOST from the list. Multiple hosts can be specified as a comma-delimited list (no whitespace around commas, please).

REX COPY−FROM

rex copy−from [OPTIONS] HOST FILE [FILE...] DEST

The copy−from command copies the requested files from HOST to the given destination DEST on the local machine. Basically, it is equivalent to running scp with proper arguments, except that it is more convenient to use if HOST doesn’t allow for passwordless authentication. In that case rex copy−from will use the authentication credentials from the rex database, as described in the subsection Login credentials, above.

The command verb rcp (an abbreviation for reverse copy), can be used instead of copy−from.

REX COPY−FROM OPTIONS
−I
, −−interactive

Interactively ask for missing usernames and passwords.

−p, −−password=PWD

Set default password (unsafe!)

−u, −−user=NAME

Set default user name.

−h, −−help

Display short help summary.

REX LOGIN

rex login [OPTIONS] HOST

Logs in to the remote host HOST. It is basically equivalent to using ssh, except that it is convenient to use if the HOST doesn’t support passwordless authentication (see the section Login credentials, above.

REX LOGIN OPTIONS
−I
, −−interactive

Interactively ask for missing usernames and passwords.

−p, −−password=PWD

Set default password (unsafe!)

−u, −−user=NAME

Set default user name.

−Z, −−zsh−quirk

Try to cope with hosts running zsh(1). See the description of this option in subsection REX RUN OPTIONS.

−h, −−help

Display short help summary.

REX LIST

rex list [groups]

rex list OPTIONS hosts

List hostgroups or hosts in a hostgroup (second form).

The output of rex list groups consists of two columns: the group name and its description.

The second form lists hosts in a hostgroup selected by OPTIONS. At least one option must be present

REX LIST OPTIONS
−h
, −−help

Display short help summary. −H, −−host=HOST[,NAME...] Add HOST to the list. Multiple hosts can be specified as a comma-delimited list (no whitespace around commas, please).

−i, −−ignore-hosts

Ignore the list of hosts read from the hostgroup file. Operate only on hosts supplied in the command line (see the −−host option, above). This is useful to preserve the settings from the hostgroup file while executing the command on the hosts defined on the command line.

−X, −−exclude−host=HOST[,NAME...]

Remove HOST from the list. Multiple hosts can be specified as a comma-delimited list (no whitespace around commas, please).

Additionally, the −h, or −−help option displays a short help summary.

REX EDIT

rex edit [FILE]

Stars the editor defined by the VISUAL (or, if it is unset, EDITOR) environment variable for editing the rex database file FILE (or ~/.rex/db, if used without argument). Upon exit from the editor, it compares the new content with the existing one. If changed, the user is prompted whether they wish to save the changes.

CONFIG ARRAY

The config variable is an associative array keeping the configuration of rex. The rc scripts are free to modify it as they see fit. The valid keys in config are:

data

(list) A list of file names to copy to each host prior to running the command. See the description of the −−data−file option.

debug

(integer) Debug verbosity level. Defaults to 0, it is increased by one with each −d (−−debug) option. Biggest possible value is 3.

earlycmd

(list) A list of commands to send as early as the very first line of output from the host is seen (see the note about ZSH, below).

exclude_hosts

List of host names to exclude from processing. Normally set via the −X exclude option.

file

(string) Name of the file to read instead of the default configuration files.

hosts

List of hosts to run command on.

mode

Operation mode. The value is one of: command, copy-from, copy-to, and shell.

pass

Password to use when no host or group-specific one is given (see Login credentials).

prompt

Regular expression for matching the command line prompt. Default is "(%|#|\$) $" .

shrc

A list of commands to send after the initial command line prompt has been received. See the note about Disabling command history for an example of its use.

sudo

The string "sudo", if the command must be executed with super-user privileges (via sudo(9)). An empty string otherwise.

user

User login name to use (see Login credentials). Defaults to the value of the environment variable USER.

option,buffer-output

Buffer server output and print it only when the batch job is finished. See the −q (−−buffer−output) option.

option,confirm

(boolean) Prompt and wait for confirmation before each host. See the −w, −−confirm option.

option,editdb

(boolean) Editdb mode. See the −−editdb option.

option,encrypt

(boolean) String encrypt mode. See the encrypt option.

option,hostgroup

Name of the hostgroup as supplied by the −g (−−group) option.

option,ignore-hosts

(boolean) Ignore the list of hosts read from the hostgroup file. Set by the −i (−−ignore−hosts) command line option.

option,interactive

Set by the −I (−−interactive) option.

option,jobs

(integer) Number of hosts to process in one batch. Default is 1. See the −j (−−jobs) option.

option,log

(boolean) If set to 1, log entire output from each server on standard out. This is equivalent to setting log_user 1 in expect.

option,no-init-file

(boolean Don’t read initialization files (Configuration files). See also the −q (−−no−init−file) option.

option,no-host-header

(boolean) Don’t print hostname before output from the host (the −−no−host−header option).

option,noop

(boolean) Don’t run COMMAND. This option is convenient when you have some side effects in your rc file (such as, e.g. launching a vpn etc.) and wish to evaluate them without actually executing a command.

option,prefix

(boolean) Prefix each output line with the host name or IP. See the −P (−−prefix) option.

option,script

(boolean) True if command is a local script (see the −−script option).

option,source

Base name of the user-defined TCL script to be sourced. See the −−source option.

option,resolve

(boolean) Resolve host IP addresses into the hostnames. Default is 1. Reset via the −n, −−no−resolve command line option.

option,verbose

(boolean) Print additional warnings (−v, −−verbose).

option,zsh-quirk

(boolean) Try to cope with remote zsh(1) shells. See the description of the −Z (−−zsh−quirk) option, and the subsection ZSH in the NOTES section, below.

REX DATABASE

Rex searches for its database file in the following locations:
/etc/rex/db

Site-wide database file.

~/.rex/db

Per-user database file.

Existing files are loaded in that order, so that per-user settings override the system-wide ones. Each db file is a textual file with key-value pairs separated by any amount of whitespace. Each pair occupies a separate line. Empty lines and comments (starting with #) are ignored.

The format of the key value is:

[GROUP:][HOST:]KEYWORD

(square brackets denoting optional parts). The reserved keywords are:

user

User login name.

pass

User password.

earlycmd

Commands to send as early as the very first line of output from the host is seen. The value is a whitespace-separated list of TCL strings. Please use curly braces, instead of double quotes, to prevent interpretation of the string value.

This setting is useful if the command line prompt cannot be easily recognized (see the note about ZSH, below).

shrc

Commands to send after the initial command line prompt has been received. The value is a whitespace-separated list of TCL strings. Please use curly braces, instead of double quotes, to prevent interpretation of the string value.

See the note about Disabling command history for an example of its use.

Users can define their own keywords.

NOTES

Disabling command history
You might wish to disable the command history on remote hosts for commands executed by rex. Use the shrc setting for that. This setting supplies a list of commands rex will send after it has received the initial command line prompt from the remote machine.

The exact list of commands depends on the shell that the remote uses.

The simplest way, common for bash, ksh, and zsh is:

shrc HISTFILE=/dev/null

Similar setting for csh(1) or tcsh(1) is:

shrc {set histfile=/dev/null}

The drawback of this approach that the assignment itself, and all the built-in commands sent by rex itself are still retained in history.

A more sophisticated way, suitable for both bash and zsh shells is:

shrc {
     if test −n "$HISTFILE" && test −f "$HISTFILE"; \
     then \
       mv $HISTFILE ${HISTFILE}~; \
       head −n −1 ${HISTFILE}~ > $HISTFILE; \
     fi} \
     {unset HISTFILE}

It removes the most recent line from the history file and unsets the HISTFILE variable, thereby preventing the shell from further updating it.

(The most recent line contains the command stty −echo, sent by rex at the beginning of each session.)

To set history cleaning on a per-host (or per-hostgroup) basis, use the shrc key in the rex database file.

ZSH
Interaction with zsh(1) poses considerable problems because it spits out enormous amounts of escape sequences for colorization and other purposes, which makes it next to impossible to write an efficient regular expression for >recognizing command line prompts. To make matters even worse, it ignores any changes made by stty.

An ad-hoc way of coping with hosts running zsh is provided by the −Z (−−zsh−quirk) command line option. However, it is convenient only for casual usage, because of the slowdown it imposes.

The proper way of handling zsh hosts is by configuring the earlycmd setting. This configuration setting declares a list of commands that rex is to send as early as it sees the very first line of output from the host.

If all your hosts run zsh, add the following to your rc file:

ifmode {
  run {
    environ TERM=dumb
  }
}
earlycmd {unsetopt ZLE} {PS1=’$ ’}

This will disable the zle module, which is the cause of all evil (TM), reset terminal defaults to decent values and set a proper command line prompt.

If only some of your hosts run zsh, you can set the earlycmd option in the rex database file, using the earlycmd key, either for hostgroup or for individual hosts.

The value of that option is a whitespace-separated list of TCL strings.

For example, if the account on host baboo runs zsh, start rex --editdb and add the following line:

baboo:earlycmd   {unsetopt ZLE} {PS1=’$ ’}

Notice that you will still need to have

environ TERM=dumb

in your rc file.

FILES

/etc/rex/rc

System-wide configuration file.

~/.rex/rc

User-specific configuration file.

/etc/rex/db

System-wide database file (see Login credentials).

~/.rex/db

User-specific database file.

/etc/rex/script

System-wide script directory (see the subsection Scripting, above).

~/.rex/script

User-specific script directory.

/etc/rex/hostgroup/GROUP/script

System-wide hostgroup-specific script directory.

~/.rex/hostgroup/GROUP/script

Per-user hostgroup-specific script directory.

/etc/rex/hostgroup/GROUP/rc

System-wide definition of GROUP.

~/.rex/hostgroup/GROUP/rc

User-specific definition of GROUP.

/etc/rex/hostgroup/GROUP/description

System-wide description of GROUP.

~/.rex/hostgroup/GROUP/description

User-specific description of GROUP.

ENVIRONMENT

EXPECT_DEBUG

Enables detailed diagnostic output of internal activity of commands such as expect and interact. The value of this variable is the name of a file where to output additional information (as well as showing it on the standard error). E.g., setting EXPECT_DEBUG=foo is similar to using exp_internal -f foo 1 at the beginning of the expect code.

EXPECT_PROMPT

Regular expression for matching command line prompt. Default is "(%|#|\$) $" .

VISUAL

Pathname of the editor binary.

EDITOR

Pathname of the editor binary. It is used if VISUAL is not defined.

USER

Name of the current user. See also the −u, −−user option.

RETURN VALUE

0

Success.

1

Command line usage error.

2

Some of hosts were unreachable or refused connection.

EXAMPLE

1.

Check uptime on all hosts in group web:

rex run -g web uptime

2.

Same with single-line output for each host.

rex run −g web −−prefix −−no−host−header uptime

3.

Restart httpd on each host (notice the use of sudo).

rex run −g web sudo /etc/init.d/httpd restart

AUTHORS

Sergey Poznyakoff

BUG REPORTS

Report bugs to <gray+rex@gnu.org.ua>.

COPYRIGHT

Copyright © 2012−2016 Sergey Poznyakoff
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.


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