printing my own message as each command in a bash script has completed successfully

CoffeeKing!!! · 01-25-2009, 11:27 PM

I would like to print my own messages as each command finishes with success. Something like "foo has been moved", "~/foo_foo has been removed", foo_foo_foo has been copied"
an example:

Code:

#!/bin/bash

mv foo &&
rm ~/foo_foo&&
cp foo_foo_foo

exit

laitcg · 01-25-2009, 11:45 PM

echo "Hello World!"

Might I recommend the Advanced Bash Scripting Guide: http://tldp.org/LDP/abs/html/

David the H. · 01-26-2009, 12:13 AM

A slightly better way that ensures that the action was actually completed first:

Code:

if [ "$?" = "0" ]; then
   echo "success"
else
   echo "fail"
fi

This tests the exit code of the last executed command, and prints an appropriate message depending on if it's zero (success), or not (fail).

Edit: Here's a streamlined version you can tack onto the end of a command for single-line use.

Code:

mv foo && echo "success" || echo "fail"

CoffeeKing!!! · 01-26-2009, 12:37 AM

Quote:

Originally Posted by David the H.

A slightly better way that ensures that the action was actually completed first:

Code:

if [ "$?" = "0" ]; then
   echo "success"
else
   echo "fail"
fi

This tests the exit code of the last executed command, and prints an appropriate message depending on if it's zero (success), or not (fail).

Edit: Here's a streamlined version you can tack onto the end of a command for single-line use.

Code:

mv foo && echo "success" || echo "fail"

Thanks David. What about if I wanted to display a message until the file finished moving and then display if it was successful or not?

CoffeeKing!!! · 01-26-2009, 12:45 AM

with this

Code:

#! /bin/bash
# cp.sh

while cp archives.tar archives2.tar
 do echo "copying"
   if [ "$?" = "0" ]; then
   echo "success"
else
   echo "fail"
fi
exit

I am getting an error:

./cp.sh: line 11: syntax error: unexpected end of file

CoffeeKing!!! · 01-26-2009, 01:21 AM

now I'm only getting the success message :

Code:

#! /bin/bash

cp archives.tar archives2.tar
while [ "$?" != "0" ];
   do
       echo "copying"
   done
if [ "$?" = "0" ]; then
   echo "success"
else
   echo "fail"
fi

CoffeeKing!!! · 01-26-2009, 01:31 AM

tried this but "copying" does not display as the file is copying. Any suggestions?

Code:

#! /bin/bash

cp archives.tar archives2.tar
while [ "$?" != "0" ];
   do
       echo "copying"
   done
if [ "$?" = "0" ]; then
   echo "success"
else
   echo "fail"
fi

David the H. · 01-26-2009, 02:36 AM

I don't think any of those will work. You don't get an exit code until after the process is complete, so you can't test for it until then. Also, most bash actions are run sequentially, so it's not a simple task to get two operations going at the same time (such as testing the status while the program is running). Finally, $? outputs the exit status of the last command run in that shell, so it will be testing whatever you did before the loop.

In most cases, all you really need to do is echo a line before the command stating that you're starting the job, then output the exit status afterwards. That's what most people do.

Code:

echo "copying file foo"

cp foo foo_foo && echo "file foo copied" || "failed to copy file foo"

colucix · 01-26-2009, 02:58 AM

Just an aside note: the exit status can be treated as a numerical value and the correct way to check it is to use the integer comparison operator:

Code:

if [ $? -eq 0 ]
then
   echo success
fi

Another way to use the if/then test is for testing commands (not expressions) so that you can do something like this:

Code:

if cp archives.tar archives2.tar
then
  echo success
else
  echo failed
fi

in this case the exit code of the command is still evaluated, but you embed the command and the test in a single construct.

CoffeeKing!!! · 01-26-2009, 11:02 AM

thanks guys