calling multiple functions from within if statement

Grobe · 04-13-2024, 09:08 AM

Hi.

I have this sample/training bash file that is supposed to check username and computer name.

There is something making this bash file not working correctly. But I'm not able to figure exact what that is.

I've put comments in the script to explain the problem(s)

Code:

#!/bin/bash

username=$(whoami)
thisComputerHostname=$(hostname)

function staticControlUsername () {
	if [ $username != 'grobe' ]; then
		echo 'WARNING: Pohibited from running, not logged in as correct user'
		echo 'Your login name ' $username
		return 0
	else
		echo 'INFO: User granted to run script (test 1)'
		echo 'Your login name ' $username
		return 1
	fi
}

function staticControlMachineName () {
	if [ $thisComputerHostname != 'resirkulert-Acer' ]; then
		echo 'WARNING: Pohibited from running, the computer name are incorrect'
		echo 'Current computer name:' $thisComputerHostname
		return 0
	else
		echo 'INFO: User granted to run script (test 2)'
		echo 'Name of current computer:' $thisComputerHostname
		return 1
	fi
}


# Those function call gives error when executed
#if [ staticControlUsername -a staticControlMachineName ]; then
#if [ staticControlUsername -eq 1 -a staticControlMachineName -eq 1 ]; then
#if [ [ staticControlUsername ] -a [ staticControlMachineName ] ]; then

# This returns 'Looks good' when executed, but doesn't print echo from within the functions, indicating
# that the functions isn't actually executed.'
if [ staticControlUsername ] && [ staticControlMachineName ] ; then
	echo 'Looks good'
else
	echo 'At least one test failed...'
fi

boughtonp · 04-13-2024, 09:21 AM

"[ expression ]" is an alias for "test expression" which evaluates an expression, not a command.

To evaluate the exit status of a command, remove the brackets.

See:
//www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html
//www.gnu.org/software/bash/manual/html_node/Bourne-Shell-Builtins.html#index-test

Also, using ShellCheck to identify issues is always a good idea.

Grobe · 04-13-2024, 10:25 AM

Quote:

Originally Posted by boughtonp

"[ expression ]" is an alias for "test expression" which evaluates an expression, not a command.

To evaluate the exit status of a command, remove the brackets.

See:
//www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html
//www.gnu.org/software/bash/manual/html_node/Bourne-Shell-Builtins.html#index-test

Also, using ShellCheck to identify issues is always a good idea.

Thanks, I did the shellcheck.net but this only gave corrections on quotes.

It seems to work better now, but it still doesn't work as intended:

Updated code (only line 38 is edited)

Code:

#!/bin/bash

username=$(whoami)
thisComputerHostname=$(hostname)

function staticControlUsername () {
	if [ $username != 'grobe' ]; then
		echo 'WARNING: Pohibited from running, not logged in as correct user'
		echo 'Your login name ' $username
		return 0
	else
		echo 'INFO: User granted to run script (test 1)'
		echo 'Your login name ' $username
		return 1
	fi
}

function staticControlMachineName () {
	if [ $thisComputerHostname != 'resirkulert-Acer' ]; then
		echo 'WARNING: Pohibited from running, the computer name are incorrect'
		echo 'Current computer name:' $thisComputerHostname
		return 0
	else
		echo 'INFO: User granted to run script (test 2)'
		echo 'Name of current computer:' $thisComputerHostname
		return 1
	fi
}


# Those function call gives error when executed
#if [ staticControlUsername -a staticControlMachineName ]; then
#if [ staticControlUsername -eq 1 -a staticControlMachineName -eq 1 ]; then
#if [ [ staticControlUsername ] -a [ staticControlMachineName ] ]; then

# This returns 'Looks good' when executed, but doesn't print echo from within the functions, indicating
# that the functions isn't actually executed.'
if staticControlUsername && staticControlMachineName ; then
	echo 'Looks good'
else
	echo 'At least one test failed...'
fi

On my end, both username and computer name is tested correct, but the script still runs wrong - details:

Line 12 and 13 executes normally
Line 41 wrongly execute - Line 39 is expected to execute but doesn't
Line 24 and 25 expected to execute but doesn't - neither does line 20/21.

The script seems to run as if the if the function staticControlUsername was returning 0, but it shouldn't.

MadeInGermany · 04-13-2024, 10:26 AM

In other words, a function is like a command.
And the if takes a command.

Code:

if staticControlUsername && staticControlMachineName
then
  ...
fi

Further, in the shell 0 is the success return code, 1 is a failure.
You can as well return the exit status of a true/false command.

Code:

true; return

or

Code:

false; return

boughtonp · 04-13-2024, 10:38 AM

Quote:

Originally Posted by Grobe

The script seems to run as if the if the function staticControlUsername was returning 0, but it shouldn't.

Re-read the first piece of documentation I linked, paying careful attention to the terms "zero" and "non-zero", specifically:

Quote:

The test-commands list is executed, and if its return status is zero, the consequent-commands list is executed.
,..
If ‘else alternate-consequents’ is present, and the final command in the final if or elif clause has a non-zero exit status, then alternate-consequents is executed.

With exit statuses, zero means success, non-zero means failure.

Grobe · 04-13-2024, 10:51 AM

Quote:

Originally Posted by MadeInGermany

Further, in the shell 0 is the success return code, 1 is a failure.
You can as well return the exit status of a true/false command.

Ah, THIS is where I was thinking wrong about the concept. Thank you very much for that info, after I inverted all the return codes in functions, the script behaved as expected.

So the misconception I have is coming from earlier (a life before Linux) I played around with Authohotkey script and the wbs script that was including in MS os. In those script languages, any call to a function, where the call is part of an if-statement, is normally treated as true for any number or non-zero strings. And this use for function calls therefore follows other rules.

murugesandins · 04-16-2024, 05:48 AM

Code:

#!/bin/bash
#I thought of sharing my thought.
#I always use full path
if [[ ! -f /usr/bin/whoami ]]
then
	echo /usr/bin/whoami file not found
elif [[ ! -f /usr/bin/hostname ]]
then
	echo /usr/bin/hostname file not found
else
	#you can use export if using this variable using awk/gawk/gawk.exe
	username=$(/usr/bin/whoami)
	thisComputerHostname=$(/usr/bin/hostname)
	#if some other included before this line other script could have defined alias. Hence using unalias and unset -f
	unalias staticControlUsername >/dev/null 2>&1
	unset -f staticControlUsername
	function staticControlUsername()
	{
		if [[ "$username" != "grobe" ]]
		then
			echo "WARNING: Pohibited from running, not logged in as correct user"
			echo "Your login name  $username"
			#return 1 fail result
			return 1
		else
			echo "INFO: User granted to run script (test 1)"
			echo "Your login name  $username"
			#return 0 pass result
			return 0
		fi
	}
	unalias staticControlMachineName >/dev/null 2>&1
	unset -f staticControlMachineName
	function staticControlMachineName()
	{
		#Better to use [[ .. ]] to have multiple conditional readable condition
		if [[ "$thisComputerHostname" != "resirkulert-Acer" ]]
		then
			echo "WARNING: Pohibited from running, the computer name are incorrect"
			echo "Current computer name: $thisComputerHostname"
			return 0
		else
			echo "INFO: User granted to run script (test 2)"
			echo "Name of current computer: $thisComputerHostname"
			return 1
		fi
	}
	# ========= OLD COMMENTS SHARED BY YOU =========
	# Those function call gives error when executed
	#if [[ staticControlUsername -a staticControlMachineName ]; then
	#if [[ staticControlUsername -eq 1 -a staticControlMachineName -eq 1 ]; then
	#if [[ staticControlUsername -a staticControlMachineName ]]; then
	# This returns "Looks good" when executed, but doesn't print echo from within the functions, indicating
	# that the functions isn't actually executed.
	# ========= OLD COMMENTS SHARED BY YOU =========
	if [[ 0 -eq $# ]]
	then
		staticControlUsername
	else
		staticControlUsername $@
	fi
	staticControlUsernameRet=$?
	if [[ 0 -eq $staticControlUsernameRet ]]
	then
		if [[ 0 -eq $# ]]
		then
			staticControlMachineName
		else
			staticControlMachineName $@
		fi
		staticControlMachineNameRet=$?
		if [[ 0 -eq $staticControlMachineNameRet ]]
		then
			echo "Looks good"
		else
			echo "staticControlMachineName test failed..."
		fi
	else
		echo "staticControlUsername test failed..."
	fi
fi
# COMMENTS
# Example at return values using cygwin bash.exe at Windows 11:
# $ /usr/bin/ls.exe /usr/bin/ls
# $ echo $?
# 0
# $ /usr/bin/ls.exe invalidfile.txt >/dev/null 2>&1
# $ echo $?
# 2
# $ /usr/bin/file.exe /cygdrive/c/Users/murugesan_openssl | /usr/bin/grep file
# $ echo $?
# 1
# $ /usr/bin/file /cygdrive/c/Users/murugesan_openssl | /usr/bin/grep.exe directory
# /cygdrive/c/Users/murugesan_openssl: directory
# $ echo $?
# 0

Grobe · 04-16-2024, 12:32 PM

Putting the function declaration within an if statement is new for me. I think I must try to wrap my mind around this now

pan64 · 04-16-2024, 12:55 PM

Quote:

Originally Posted by Grobe

Putting the function declaration within an if statement is new for me. I think I must try to wrap my mind around this now

forget it, it is not a good idea. That will only make the script unmaintainable.

murugesandins · 04-16-2024, 01:05 PM

Quote:

Originally Posted by Grobe

Putting the function declaration within an if statement is new for me. I think I must try to wrap my mind around this now

I agree this is difficult for 1/2/3/few months during startup.
I am having printpassbook.sh shell script from 2003 till now.
Before modification I used to take a backup of that file
After modification I used to gzip that backup file.
printpassbook.sh used to display:
1) my post office transactions (incoming/outgoing +/- four days from today
2) available balance that I can withdraw excluding recurring deposit amount and MAB
3) MIS interest I am going to receive tomorrow and day after tomorrow
4) my total salary from MIS at post office for current month
5) waiting day/month/years at RD/MIS accounts.
6) displaying related colors based on date/waiting day/month/years.

Remember to take backup before modification for maintenance.

chrism01 · 04-17-2024, 01:37 AM

I'm with pan64 - don't do that