UNIX for Dummies Questions & Answers

Hello,

I would like to change my setting in a file to the setting that user input.

For example, by default it is

Code:

ONBOOT=ON

When user key in "YES", it would be

Code:

ONBOOT=YES

--------------

This code only adds in the entire user input, but didn't replace it.

How do i go about replacing it?

Code:

echo "ONBOOT="$USERINPUT >> /etc/myfile

Regards,

Malfolozy

Moderator's Comments:

CODE tags are for sample input and output as well as for code.

If this is the only thing in the file, change:

Code:

echo "ONBOOT="$USERINPUT >> /etc/myfile

to:

Code:

echo "ONBOOT=$USERINPUT" > /etc/myfile

Hello,

Basically, the file that i wanted to edit is the /etc/sysconfig/network-scripts/ifcfg-eth0. Therefore, there are more than just one thing inside.

Regards,

Malfolozy

One simple way that should work on any UNIX or Linux system is (as long as the file you're editing is a non-empty text file):

Code:

#!/bin/ksh
val=${1:-YES}
file=${2:-/etc/sysconfig/network-scripts/ifcfg-eth0}
ed -s "$file" <<-EOF
	g/^ONBOOT=/d
	i
	ONBOOT=$val
	.
	w
	q
EOF

This will replace an ONBOOT= line if there is one and add the desired line if there isn't one.

Hello, the code does'nt seems to be working as it doesn't change anything in the file.

Code:

whiptail --title "Abc" --menu "Your choice" 16 78 5 \
"1)" "ONBOOT" 2>somefile

CHOICE=$(cat somefile)
case $CHOICE in
"1)") ANSWER=$(whiptail --inputbox "Yes or no?" 8 78 --title "Example" dialog" 3>&1 1>&2 2>&3)

exitstatus=$?
if [ $exitstatus = 0 ]; then 

file=${2:-/etc/sysconfig/network-scripts/ifcfg-eth0}
ed -s "$file" <<-EOF
	g/^ONBOOT=/d
	i
	ONBOOT=$ANSWER
	.
	w
	q
EOF

else

echo "ABC"

fi;;
esac

my code are as such, can you spot the mistake?

Regards,

Malfolozy

Instead of asking us to guess what is wrong with your script, why don't you show us (in CODE tags) the diagnostics that were printed when you ran your script? What output did you get? What output were you expecting? How did you respond to the whiptail commands? (In other words, why not give us the very basic information needed to determine what went wrong?)

You are not checking the exit status of the whiptail command on lines 1 and 2.

You have mismatched double quotes on line 6.

What is the 2nd argument you are passing to your script? How are you invoking your script? What OS are you using? If you aren't specifying a shell when you invoke your script, what is the default shell for your OS?

I would guess that the mismatched quotes on line 6 are your immediate problem and the other issues may be important after you fix line 6.

Is my guess close???

Please get into the habit of using indentation to make the structure of your code obvious.

The whiptail man page says that if the user selects No or Cancel from several of the options that give you choices, the exit status is 1; and if there is an error the exit status is -1. Despite what the whiptail man page says, there is no such thing as a negative exit code. If you want to explicitly look for the exit code that the whiptail man page says is -1, look for 255 instead. Nonetheless, get into the habit of checking for errors from the commands you run.

Also, get into the habit of verifying that user supplied input is appropriate rather than assuming that anything a user types is always correct.

You might want to try something more like:

Code:

#!/bin/ksh
whiptail --title "Abc" --menu "Your choice" 16 78 5 \
	"1)" "ONBOOT" 2>somefile
exitstatus=$?
if [ $exitstatus -eq 0 ]
then	read CHOICE < somefile
elif [ $exitstatus -eq 1 ]
then	echo 'User selected Cancel'
	exit 0
else	echo '1st whiptail failed'
	exit 1
fi
case $CHOICE in
"1)")	ANSWER=$(whiptail --inputbox "YES or NO?" 8 78 "YES" \
		--title "Example dialog" 3>&1 1>&2 2>&3)
	exitstatus=$?
	if [ $exitstatus -eq 0 ]
	then	# You should verify that $ANSWER is legitimate here before using it.
		file=/etc/sysconfig/network-scripts/ifcfg-eth0
		ed -s "$file" <<-EOF
			g/^ONBOOT=/d
			i
			ONBOOT=$ANSWER
			.
			w
			q
		EOF
		# You should check the exit status from ed here.  If ed fails the
		# diagnostic it prints could just be "?" which could leave users
		# wondering what happened.  So, if ed failed, print a clear
		# diagnostic message.
	elif [ $exitstatus -eq 1
	then	echo "ABC"
		exit 0
	else	echo '2nd whiptail failed'
		exit 1
	fi;;
esac

Unfortunately, since I don't have whiptail on my system, this is partially untested code.