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Full Discussion: Expect script hangs Linux
Top Forums Shell Programming and Scripting Expect script hangs Linux Post 302544541 by mass85 on Thursday 4th of August 2011 05:49:22 AM
Old 08-04-2011
Expect script hangs Linux
When I run script listed below it causes my Linux to hang. When it freezes I can do totally nothing, move cursor, switch to another terminal or whatever. Linux is just not responding and the only way out I know is a hard reset of PC.
Code:
#!/bin/bash
if [ $# -ne 1 ]; then
  echo "one parameter is needed: IP address of gateway"
  exit 1
fi

expect -d -c "
  spawn tftp $1
  expect \"tftp> \";
  send \"get /var/lib/tftpboot/fb0\\n\";
  expect {
    timeout {close; exit 1}
    \"tftp> \";    
  }
  send \"quit\\n\";
  #expect eof;
  close;
 "
echo RESULT_CODE $?

The problem occurs sometimes after first try of running this script, sometimes after second or third. Here is the output from my console in case of freeze:

Code:
$ ./dw_test.sh 192.168.1.122
expect version 5.43.0
spawn tftp 192.168.1.122
parent: waiting for sync byte
parent: telling child to go ahead
parent: now unsynchronized from child
spawn: returns {1394}

expect: does "" (spawn_id exp6) match glob pattern "tftp> "? no
tftp>
expect: does "tftp> " (spawn_id exp6) match glob pattern "tftp> "? yes
expect: set expect_out(0,string) "tftp> "
expect: set expect_out(spawn_id) "exp6"
expect: set expect_out(buffer) "tftp> "
send: sending "get /var/lib/tftpboot/fb0\n" to { exp6 }

expect: does "" (spawn_id exp6) match glob pattern "tftp> "? no
get /var/lib/tftpboot/fb0

expect: does "get /var/lib/tftpboot/fb0\r\n" (spawn_id exp6) match glob pattern "tftp> "? no

If I uncomment "expect eof;" in script, this problem does not occur. It does not occur also, when "expect eof;" is commented together with send \"quit\\n\";. Just like the tftp "quit" command caused this problem.

What is the reason for this?
Last edited by pludi; 08-04-2011 at 08:15 AM..
 

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LEARN ABOUT OPENSOLARIS

script

script(1)							   User Commands							 script(1)

NAME

       script - make record of a terminal session

SYNOPSIS

       script [-a] [filename]

DESCRIPTION

       The  script  utility  makes a record of everything printed on your screen. The record is written to filename. If no file name is given, the
       record is saved in the file typescript. See WARNINGS.

       The script command forks and creates a sub-shell, according to the value of $SHELL, and records the text from this session. The script ends
       when the forked shell exits or when Control-d is typed.

OPTIONS

       The following option is supported:

       -a    Appends the session record to filename, rather than overwriting it.

NOTES

       script places everything that appears on the screen in filename, including prompts.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |CSI			     |Enabled			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       attributes(5)

WARNINGS

       script  can  pose  a  security risk when used in directories that are writable by other users (for example, /tmp), especially when run by a
       privileged user, that is, root. Be sure that typescript is not a link before running script.

SunOS 5.11							    30 Jan 2004 							 script(1)
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