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Top Forums Shell Programming and Scripting SSH sessions from bash script Post 302307130 by qneill on Tuesday 14th of April 2009 04:40:39 PM
Old 04-14-2009
No reason you have to use a "here script" with <<EOF, you can pipe commands directly to the standard input of ssh, for example using echo:

Code:
$ D=/tmp; F1=x1; echo "F2=$D/$F1
echo on \$(hostname): escaped: D=\$D F1=\$F1 F2=\$F2
echo on \$(hostname): not escaped: D=$D F1=$F1 F2=$F2
df $D >\$F2; ls -l \$F2; cat \$F2; rm -rf \$F2; ls -l \$F2
" | ssh qneill@qneill-linux

this shows a couple of local variables D and F1 (expanded locally when the local echo is executed), and a remote variable F2 (expands to nothing locally, but remotely expands to the assigned value). The commands produce this output:

Code:
on qneill-linux: escaped: D= F1= F2=/tmp/x1
on qneill-linux: not escaped: D=/tmp F1=x1 F2=
-rw-r--r-- 1 qneill 30101 125 2009-04-14 15:25 /tmp/x1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda1            147581948  78980980  61104240  57% /
ls: /tmp/x1: No such file or directory

The commands shown use the local variable D and remote variable F2, creating, using, and removing a file (/tmp/x1 on the remote machine).

If all of your variable expansions are constant, or only depend on remote things, you can use single quotes and avoid having to escape all the $ signs:

Code:
echo 'D=/tmp; F1=x1; F2=$D/$F1
echo on $(hostname): D=$D F1=$F1 F2=$F2
df $D >$F2; ls -l $F2; cat $F2; rm -rf $F2; ls -l $F2
' | ssh qneill@qneill-linux

which yields
Code:
on qneill-linux: D=/tmp F1=x1 F2=/tmp/x1
-rw-r--r-- 1 qneill 30101 125 2009-04-14 15:34 /tmp/x1
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda1            147581948  78980960  61104260  57% /
ls: /tmp/x1: No such file or directory

Once you start using this mechanism for anything complicated, you will quickly run into many quoting issues. Consider writing a script that generates code on the remote system, or a templated script that can be parameterized locally or remotely as needed, then executed remotely with a single call to ssh.
--
qneill
 

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SCRIPT(1)                                                          User Commands                                                         SCRIPT(1)

NAME
script - make typescript of terminal session SYNOPSIS
script [options] [file] DESCRIPTION
script makes a typescript of everything displayed on your terminal. It is useful for students who need a hardcopy record of an interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1). If the argument file is given, script saves the dialogue in this file. If no filename is given, the dialogue is saved in the file type- script. OPTIONS
-a, --append Append the output to file or to typescript, retaining the prior contents. -c, --command command Run the command rather than an interactive shell. This makes it easy for a script to capture the output of a program that behaves differently when its stdout is not a tty. -e, --return Return the exit code of the child process. Uses the same format as bash termination on signal termination exit code is 128+n. -f, --flush Flush output after each write. This is nice for telecooperation: one person does `mkfifo foo; script -f foo', and another can supervise real-time what is being done using `cat foo'. --force Allow the default output destination, i.e. the typescript file, to be a hard or symbolic link. The command will follow a symbolic link. -q, --quiet Be quiet (do not write start and done messages to standard output). -t[file], --timing[=file] Output timing data to standard error, or to file when given. This data contains two fields, separated by a space. The first field indicates how much time elapsed since the previous output. The second field indicates how many characters were output this time. This information can be used to replay typescripts with realistic typing and output delays. -V, --version Display version information and exit. -h, --help Display help text and exit. NOTES
The script ends when the forked shell exits (a control-D for the Bourne shell (sh(1)), and exit, logout or control-d (if ignoreeof is not set) for the C-shell, csh(1)). Certain interactive commands, such as vi(1), create garbage in the typescript file. script works best with commands that do not manipulate the screen, the results are meant to emulate a hardcopy terminal. It is not recommended to run script in non-interactive shells. The inner shell of script is always interactive, and this could lead to unexpected results. If you use script in the shell initialization file, you have to avoid entering an infinite loop. You can use for example the .profile file, which is read by login shells only: if test -t 0 ; then script exit fi You should also avoid use of script in command pipes, as script can read more input than you would expect. ENVIRONMENT
The following environment variable is utilized by script: SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most shells set this variable automatically). SEE ALSO
csh(1) (for the history mechanism), scriptreplay(1) HISTORY
The script command appeared in 3.0BSD. BUGS
script places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects. script is primarily designed for interactive terminal sessions. When stdin is not a terminal (for example: echo foo | script), then the session can hang, because the interactive shell within the script session misses EOF and script has no clue when to close the session. See the NOTES section for more information. AVAILABILITY
The script command is part of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils /util-linux/>. util-linux June 2014 SCRIPT(1)
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