Bash – How to use Expect in a Bash script

bashexpect

I am trying to write a script that pulls the latest version of my software from a Git repository and updates the configuration files. When pulling from the repository though, I have to enter a password. I want the script to automate everything, so I need it to automatically fill it in for me. I found this site that explained how to use Expect to look for the password prompt and send the password. I can't get it to work though.

Here's my script:

#!/usr/bin/expect -f
set password [lrange $argv 0 0]
set timeout -1

clear
echo "Updating Source..."
cd sourcedest
git pull -f origin master

match_max 100000
# Look for passwod prompt
expect "*?assword:*"
# Send password aka $password
send -- "$password\r"
# send blank line (\r) to make sure we get back to gui
send -- "\r"
expect eof

git checkout -f master
cp Config/database.php.bak Config/database.php
cp webroot/index.php.bak webroot/index.php
cp webroot/js/config.js.bak webroot/js/config.js

What am I doing wrong?

Here's the site I got it from: http://bash.cyberciti.biz/security/expect-ssh-login-script/

Best Answer

This is pretty much taken from the comments, with a few observations of my own. But nobody seems to want to provide a real answer to this, so here goes:

Your problem is you have an Expect script and you're treating it like a Bash script. Expect doesn't know what cd, cp, and git mean. Bash does. You want a Bash script that makes a call to Expect. For example:

#!/usr/bin/env bash

password="$1"
sourcedest="path/to/sourcedest"
cd $sourcedest

echo "Updating Source..."
expect <<- DONE
  set timeout -1

  spawn git pull -f origin master
  match_max 100000

  # Look for password prompt
  expect "*?assword:*"
  # Send password aka $password
  send -- "$password\r"
  # Send blank line (\r) to make sure we get back to the GUI
  send -- "\r"
  expect eof
DONE

git checkout -f master
cp Config/database.php.bak Config/database.php
cp webroot/index.php.bak webroot/index.php
cp webroot/js/config.js.bak webroot/js/config.js

However, as larsks pointed out in the comments, you might be better off using SSH keys. Then you could get rid of the expect call altogether.

Related Solutions

Bash – How to check if a directory exists in a Bash shell script

To check if a directory exists in a shell script, you can use the following:

if [ -d "$DIRECTORY" ]; then
  # Control will enter here if $DIRECTORY exists.
fi

Or to check if a directory doesn't exist:

if [ ! -d "$DIRECTORY" ]; then
  # Control will enter here if $DIRECTORY doesn't exist.
fi

However, as Jon Ericson points out, subsequent commands may not work as intended if you do not take into account that a symbolic link to a directory will also pass this check. E.g. running this:

ln -s "$ACTUAL_DIR" "$SYMLINK"
if [ -d "$SYMLINK" ]; then 
  rmdir "$SYMLINK" 
fi

Will produce the error message:

rmdir: failed to remove `symlink': Not a directory

So symbolic links may have to be treated differently, if subsequent commands expect directories:

if [ -d "$LINK_OR_DIR" ]; then 
  if [ -L "$LINK_OR_DIR" ]; then
    # It is a symlink!
    # Symbolic link specific commands go here.
    rm "$LINK_OR_DIR"
  else
    # It's a directory!
    # Directory command goes here.
    rmdir "$LINK_OR_DIR"
  fi
fi

Take particular note of the double-quotes used to wrap the variables. The reason for this is explained by 8jean in another answer.

If the variables contain spaces or other unusual characters it will probably cause the script to fail.

Bash – How to get the source directory of a Bash script from within the script itself

#!/usr/bin/env bash

SCRIPT_DIR="$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"

is a useful one-liner which will give you the full directory name of the script no matter where it is being called from.

It will work as long as the last component of the path used to find the script is not a symlink (directory links are OK). If you also want to resolve any links to the script itself, you need a multi-line solution:

#!/usr/bin/env bash

SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink
  DIR="$( cd -P "$( dirname "$SOURCE" )" >/dev/null 2>&1 && pwd )"
  SOURCE="$(readlink "$SOURCE")"
  [[ $SOURCE != /* ]] && SOURCE="$DIR/$SOURCE" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
done
DIR="$( cd -P "$( dirname "$SOURCE" )" >/dev/null 2>&1 && pwd )"

This last one will work with any combination of aliases, source, bash -c, symlinks, etc.

Beware: if you cd to a different directory before running this snippet, the result may be incorrect!

Also, watch out for $CDPATH gotchas, and stderr output side effects if the user has smartly overridden cd to redirect output to stderr instead (including escape sequences, such as when calling update_terminal_cwd >&2 on Mac). Adding >/dev/null 2>&1 at the end of your cd command will take care of both possibilities.

To understand how it works, try running this more verbose form:

#!/usr/bin/env bash

SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink
  TARGET="$(readlink "$SOURCE")"
  if [[ $TARGET == /* ]]; then
    echo "SOURCE '$SOURCE' is an absolute symlink to '$TARGET'"
    SOURCE="$TARGET"
  else
    DIR="$( dirname "$SOURCE" )"
    echo "SOURCE '$SOURCE' is a relative symlink to '$TARGET' (relative to '$DIR')"
    SOURCE="$DIR/$TARGET" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
  fi
done
echo "SOURCE is '$SOURCE'"
RDIR="$( dirname "$SOURCE" )"
DIR="$( cd -P "$( dirname "$SOURCE" )" >/dev/null 2>&1 && pwd )"
if [ "$DIR" != "$RDIR" ]; then
  echo "DIR '$RDIR' resolves to '$DIR'"
fi
echo "DIR is '$DIR'"

And it will print something like:

SOURCE './scriptdir.sh' is a relative symlink to 'sym2/scriptdir.sh' (relative to '.')
SOURCE is './sym2/scriptdir.sh'
DIR './sym2' resolves to '/home/ubuntu/dotfiles/fo fo/real/real1/real2'
DIR is '/home/ubuntu/dotfiles/fo fo/real/real1/real2'

Best Answer

Related Solutions

Bash – How to check if a directory exists in a Bash shell script

Bash – How to get the source directory of a Bash script from within the script itself

Related Topic