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Top Forums Shell Programming and Scripting Expect Script - Variables are Empty immediately after "Setting" Them? Post 302780011 by mrm5102 on Wednesday 13th of March 2013 04:51:24 PM
Old 03-13-2013
Expect Script - Variables are Empty immediately after "Setting" Them?

Hello All,

I have embedded some expect code inside a Bash script I'm writing, but for some reason any variable I 'set' to something is
showing as empty immediately on the next line...

I haven't run into this problem before so I'm not sure what it could be...? I'm guessing it has something to do with the code
being embedded in another script..?


Here's my Code:
Code:
#!/bin/bash

echo "Here, in Bash Script"

# other stuff.....:......


/usr/bin/expect - << EOF

    set my_var "Hello World"

    puts "my_var = $my_var\n"

EOF

echo "Back from Expect Script"

exit 0

And my Output:
Code:
Here, in Bash Script
my_var = 

Back from Expect Script

Anyone know why the variables are NOT being set? I'm Stumpped..!!!
Any thoughts would be very much appreciated.


Thanks in Advance,
Matt

---------- Post updated at 04:51 PM ---------- Previous update was at 04:17 PM ----------

Figured it out...!!

You need to escape the '$' in front of any/all variables. I think this is due to using the "<<" which is open to variable expansion, so
I think that's why they need to be escaped...

So if the code is like this, it will work:
Code:
#!/bin/bash

echo "Here, in Bash Script"

# other stuff.....:......


/usr/bin/expect - << EOF

    set my_var "Hello World"

    puts "my_var = \$my_var\n"

EOF

echo "Back from Expect Script"

exit 0

*Notice the '\' in front of "\$my_var" in the puts statement...

And my Output:
Code:
Here, in Bash Script
my_var = Hello World

Back from Expect Script

Hopefully that helps someone in the same predicament I was in...

Thanks,
Matt
 

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SCRIPT(1)						    BSD General Commands Manual 						 SCRIPT(1)

NAME
script -- make typescript of terminal session SYNOPSIS
script [-a] [-c COMMAND] [-e] [-f] [-q] [-t] [file] DESCRIPTION
Script makes a typescript of everything printed 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 all dialogue in file. If no file name is given, the typescript is saved in the file typescript. Options: -a Append the output to file or typescript, retaining the prior contents. -c 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 the exit code of the child process. Uses the same format as bash termination on signal termination exit code is 128+n. -f Flush output after each write. This is nice for telecooperation: One person does `mkfifo foo; script -f foo' and another can super- vise real-time what is being done using `cat foo'. -q Be quiet. -t Output timing data to standard error. 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. The script ends when the forked shell exits (a control-D to exit 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. 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. AVAILABILITY
The script command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/. Linux July 30, 2000 Linux
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