passing command line to a BASH function

GSMD · 04-16-2007, 02:00 AM

Here's a wrapper function meant to accept a command to execute and a description.
This should "wrap" commands in a script so that user would see whether smth went wrong.

Code:

COMMAND_WRAPPER () {
	printf "%-50s" "$1"
	"`$2` 1> /tmp/ws-man.tmp 2>> /tmp/ws-man.tmp" # can't figure out how to make this work
	if [ "$?" = "0" ] # execute the command passed and evaluate the result
		then
			printf "[\E[1;32mdone"
			tput sgr0 #reset color; know this is ugly, yet to find a better solution
			printf "]\n\n"
			return 0
		else
			printf "[\E[1;31merror"
			tput sgr0 #reset color
			printf "]\n\n"
			printf "=== log start ===\n"
			cat /tmp/ws-man.tmp
			printf "\n=== log end ===\n"
			return 1
	fi
}

Now, I can't make the command get executed. I've tried numerous variants, neither worked as expected. The best thing I've got is that the command got executed with redirections treated wrong when doing smth like

Code:

COMMAND_WRAPPER "Creating SVN repo" "svnadmin create $PATH_TO_REPO"

.
Probably it's smth obvious but I'm yet another

who spent a couple of hours banging against the wall

.

TIA.

blackhole54 · 04-16-2007, 02:37 AM

A couple of prelimary comments:

Using backticks the way you are will cause the output of the command to be (attempted to be) executed. I am not sure that is what you want. (Although perhaps I misunderstand.)

I am not sure whether your redirection might cause problems since you are redirecting two streams to the same file. Since one is a ">" and the other is a ">>" I am not sure what your are trying to do. If you just want to start a new file that contains both stdout and stderr you would usually do it one of the followings ways (all three lines do the same thing):

Code:

command > somefile 2>&1
command 2> somefile 1>&2
command &> somefile

That said, I think the line you want is:

Code:

$* > /tmp/ws-man.tmp 2>&1

This assumes that the command and all of its arguments are different parameters. In other words, don't quote them together as a single argument when you call the function.

bigearsbilly · 04-16-2007, 02:49 AM

blackhole is right.

you have quoted the whole line, (and you don't need the `backticks`)
so it is read by the shell as a single program with an extremely unusual name!
including the spaces.

(which probably will not exist)

GSMD · 04-16-2007, 03:00 AM

Thanks, guys, that's an A+++ class support!
I've implemented

Code:

$2 &> /tmp/ws-man.tmp

.

GSMD · 04-16-2007, 09:18 AM

Banging against the wall again. How should I pass the string like

Code:

COMMAND_WRAPPER "Creating Trac instance" 'trac-admin "$VAR_TEAM_ROOTtrac" initenv "$TEAM $COMPANY project" "qlite:db/trac.db" "svn" "$VAR_TEAM_ROOTsvn" "$TEMPLATES_DIR"'

so that some arguments consist of multiple words?

Thanks.

GSMD · 04-17-2007, 01:27 AM

Tried various workaround but neither worked out. Like

Code:

TRAC_COMMAND='trac-admin "$VAR_TEAM_ROOT/trac" initenv "$TEAM $COMPANY project" "sqlite:db/trac.db" "svn" "$VAR_TEAM_ROOT\svn" "$TEMPLATES_DIR/trac/templates"'
COMMAND_WRAPPER "Creating Trac" $TRAC_COMMAND

blackhole54 · 04-17-2007, 01:29 AM

Complex quoting still gives me problems. With that disclaimer (after doing some experiments), I don't see anything wrong with what you are doing (in post #5) unless you need those (what appear to be) variables evaluated when you give the command COMMAND_WRAPPER. Variables are not evaluated inside single quotes. But when your function executes the command trac-admin I would think the single quotes would already be dropped and the variables would get evaluated at that time.

A couple of things you might try (no promises):

You could replace the single quotes with double quotes. If you do that, then you need to "escape" the inner double quotes with a back slashes like so:

Code:

"\"The inner double quotes here are escaped with a back slash\""

The other thing you could try is totally removing the outer (single) quotes and changing this

Code:

$2 > /tmp/ws-man.tmp

to this

Code:

shift
$* > /tmp/ws-man.tmp

The shift throws away the existing first parameter and then changes the orignal second parameter to be first, original third parameter to be second, etc.

If none of this helps, maybe if you post the error message you are getting it will help somebody figure out what is wrong.

EDIT: Clarified that this post was in response to post #5

GSMD · 04-17-2007, 01:55 AM

Blackhole, thanks for your promptly answers.
I've tried "escaping" double quotes and not using single quotes at all, but this won't help (I'd get a message that only 1 arg is passed to initenv).
For the

Code:

COMMAND_WRAPPER "Creating Trac" 'trac-admin "$VAR_TEAM_ROOT/trac" initenv "$TEAM $COMPANY project" "sqlite:db/trac.db" "svn" "$VAR_TEAM_ROOT\svn" "$TEMPLATES_DIR/trac/templates"'

i get

Code:

Wrong number of arguments to initenv: 7

so "$TEAM $COMPANY project" is obviously treated wrong. So replace it with "$TEAM_$COMPANY_project" and move a bit forward to an error telling that "$TEMPLATES_DIR/trac/templates" is not found. TEMPLATES_DIR is assigned a value right at the previous step (it's an if-then-else). Trying to assign the value manually (TEMPLATES_DIR=/etc/opt/templates) here or at the COMMAND_WRAPPER() won't help either. So I provide a value directly at the command line and finally bump into

Code:

Failed to create environment. [Errno 2] No such file or directory: '/var/opt/ws-man/sample/"$VAR_TEAM_ROOT/trac"

BTW, using "shift" won't help either.

ntubski · 04-17-2007, 11:54 AM

Try using

Code:

eval $2 &> /tmp/ws-man.tmp

with

Code:

export VAR_TEAM_ROOT=/the/team/root
export TEAM=#fill in the rest...
...
COMMAND_WRAPPER "Creating Trac" 'trac-admin "$VAR_TEAM_ROOT/trac" initenv "$TEAM $COMPANY project" "sqlite:db/trac.db" "svn" "$VAR_TEAM_ROOT/svn" "$TEMPLATES_DIR/trac/templates"'

I assume that backslash was meant to be a forward slash

GSMD · 04-19-2007, 04:34 AM

Thanks a lot, ntubski.
eval did sort things out, even w/o exporting variables involved.
And yes, that was a forward slash there.

GSMD · 04-19-2007, 07:04 AM

So that's the way the pre-final version of the function looks like:

Code:

# command wrapper; prints the text and executes commands supplied; then displays the exit status
# $1 - message to display; $* - commands to execute
COMMAND_WRAPPER () {
	printf "%-50s" "$1" # print the message
	while [ "$#" != "0" ]
	 do
		eval $1 &> /tmp/ws-man.tmp # execute the command
		shift
	done
	if [ "$?" = "0" ] # execute the command passed and evaluate the result
		then
			printf "[\E[1;32mdone"
			tput sgr0 #reset color
			printf "]\n"
			return 0
		else
			printf "[\E[1;31merror"
			tput sgr0 #reset color
			printf "]\n"
			printf "=== log start ===\n"
			cat /tmp/ws-man.tmp
			printf "\n=== log end ===\n\n"
			return 1
	fi
}

I want to drop out of the cycle if any of the commands returns an error state. So that's what I try to do:

Code:

while [ "$#" != "0" ] && [ "$?" = "0" ]
	 do
		shift
		eval $1 &> /tmp/ws-man.tmp # execute the command
	done

Yet it won't work (so the loop continues until the last argument).

Could anyone please help sort this out?

Thanks.

ntubski · 04-19-2007, 10:44 AM

$? holds the status of the last command, [ "$#" != "0" ] is a command, so when you test $? it always holds 0.

You could switch the order of the tests, but it would probably be better to save the return status immediately after doing eval.

Code:

RETURNED=0
while [ "$#" != "0" ] && [ "$RETURNED" = "0" ]
do
        shift
	eval $1 &> /tmp/ws-man.tmp # execute the command
        RETURNED=$?
done

GSMD · 04-19-2007, 11:16 AM

Thanks. To me it was not obvious, but after reading your reply I recalled that [ "some statement" ] is a shortcut to test "some statement". Thanks again, I'll try this.

cfaj · 04-19-2007, 11:22 AM

Quote:

Originally Posted by blackhole54

That said, I think the line you want is:

Code:

$* > /tmp/ws-man.tmp 2>&1

That should be:
Code:
"$@" > /tmp/ws-man.tmp 2>&1
Otherwise multiword arguments will be split. Using "$@" maintains the arguments as given on the command line.

GSMD · 04-20-2007, 02:44 AM

Instead of utilizing a variable, I just switched places:

Code:

COMMAND_WRAPPER () {
	printf "%-50s" "$1" # print the message
	while [ "$?" = "0" ] && [ "$#" != "0" ]
	 do
		shift
		eval $1 &> /tmp/ws-man.tmp # execute the command
	done
	if [ "$?" = "0" ] # execute the command passed and evaluate the result
		then
			printf "[\e[1;32mdone\e[m]\n"
			return 0
		else
			printf "[\e[1;31merror\e[m]\n"
			printf "=== log start ===\n"
			cat /tmp/ws-man.tmp
			printf "\n=== log end ===\n\n"
			return 1
	fi
}