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ch
changes the host on which subsequent commands are to be executed
SYNOPSIS
ch [-S] [-t] [host_name]
ch [-h | -V]
DESCRIPTION
Changes the host on which subsequent commands are to be executed.
By default, if no arguments are specified, changes the current host to the home
host, the host from which the ch command was issued.
By default, executes commands on the home host.
By default, shell mode support is not enabled.
By default, does not display execution time of tasks.
The ch command allows you to quickly change to a designated host with the
same execution environment. A simple shell is started that delivers all
subsequent commands (except built-in commands) to the designated host for
execution.
When the simple shell starts, it is in the current working directory and has the
same command execution environment as that of the parent shell. Every
remotely dispatched command is executed with the same environment as that
on the home host. The syntax of the ch command is similar to that of the
Bourne shell. However, there are some important differences.
The ampersand (&) following a command line (representing a background job
in the Bourne shell) is ignored by ch. You can submit background jobs in ch
with the built-in post command and bring them into the foreground with the
built-in contact command (see below for details).
ch recognizes a ~ (tilde) as a special path name. If a ~ (tilde) is followed by a
space, tab, new line or / (slash) character, then the ~ character is translated
into the user's home directory. Otherwise, the ~ is translated as the home
directory of the user name given by the string following the ~ character.
Pipelines, lists of commands and redirection of standard input/output are all
handled by invoking /bin/sh.
The following sequence of commands illustrates the behavior of the ch
command. For example, the user is currently on hostA:
% ch hostB
hostB> ch hostC
hostC> ch
hostA> ... ...
OPTIONS
-S
Starts remote tasks with shell mode support. Shell mode support is required
for running interactive shells or applications which redefine the CTRL-C and
CTRL-Z keys (for example, jove).
-t
Turns on the timing option. The amount of time each subsequent command takes to execute is displayed.
host_name
Executes subsequent commands on the specified host.
-h
Prints command usage to stderr and exits.
-V
Prints LSF release version to stderr and exits.
USAGE
The ch command interprets the following built-in commands:
cd [directory_name]
Changes the current working directory to the specified directory. If a directory is not specified, changes to the user's home directory by default.
ch [host_name]
Changes the current working host to the specified host. If a host is not specified, changes to the home host by default.
post [command [argument ...]]
Posts the specified command for execution in the background on the
current working host. ch assigns a unique task ID to this command and
displays this ID, then continues to interact with the user. However, the
output of background jobs may disturb the screen. You can post
multiple commands on one host or on different hosts. When a
previously posted command is completed, ch reports its status to the
standard error. If a command is not specified, ch displays all currently
running background commands.
contact task_ID
Brings a previously posted background command into the foreground.
task_ID is the ID returned by the post command. Standard input is
now passed to this foreground command. You cannot put an active
foreground job into the background. A command that has been
brought into the foreground with the contact command cannot be put
back into the background.
exit
Exits ch if there are no posted commands running. Typing an EOF
character (usually CTRL-D but may be set otherwise, see stty(1))
forces ch to exit; uncompleted posted commands are killed.
SEE ALSO
lsrun(1), rsh(1), stty(1)
LIMITATIONS
Currently, the ch command does not support script, history, nor alias.
The ch prompt is always the current working host:current working directory
followed by a > (right angle bracket) character. If the ch session is invoked by
a shell that supports job control (such as tcsh or ksh), CTRL-Z suspends the
whole ch session. The exit status of a command line is printed to stderr if
the status is non-zero.
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Date Modified: February 24, 2004
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