[SOLVED] shell script : if and variable

iorih0304 · 08-08-2017, 01:08 AM

Hi all.
I write a shell script to check the bios version as follow:

Code:

#!/bin/bash
# Bios version check
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
echo "BIOS version check..."
bios_ver=`dmidecode -s bios-version`

echo "Version : $bios_ver"
echo "Expected vesion : 080015"
echo "--------------------------------------"

if [ "${bios_ver}" == "080015" ]; then
        echo "Bios test : pass"
else
        echo "Bios test : fail"
fi

but the result shows fail:

Code:

BIOS version check...
Version : 080015
Expected version : 080015
--------------------------------------
Bios test : fail

I think this problem is the variable bios_ver, but I have no idea how to fix.

Thanks.

Turbocapitalist · 08-08-2017, 01:29 AM

The syntax is different from other programming languages.

Code:

if [ "${bios_ver}" = "080015" ]; then
...

Or

Code:

if [ "${bios_ver}" -eq "080015" ]; then
...

The first example is if you are going to treat it as a string. The second is if you are working with integers.

See "man test".

iorih0304 · 08-08-2017, 01:34 AM

Thank you for your help.
I try second example, it works!

dejank · 08-08-2017, 02:25 AM

It will pass no matter if you compare string or number, because in your case those are same, if you do not use curly braces. Also, you do not need quoting around variable and that number in test.

Just checked here with few things included:

Code:

dejan@ddeb:~$ bios_version=080015
dejan@ddeb:~$ if [[ $bios_version = 080015 ]] ; then  echo "pass"; else echo "fail"; fi
pass
dejan@ddeb:~$ if [[ ${bios_version} = 080015 ]] ; then  echo "pass"; else echo "fail"; fi
pass
dejan@ddeb:~$ if [[ "${bios_version}" = 080015 ]] ; then  echo "pass"; else echo "fail"; fi
pass
dejan@ddeb:~$ if [[ "${bios_version}" = "080015" ]] ; then  echo "pass"; else echo "fail"; fi
pass
dejan@ddeb:~$ if [ "${bios_version}" = "080015" ] ; then  echo "pass"; else echo "fail"; fi
pass
dejan@ddeb:~$ if [ "${bios_version}" == "080015" ] ; then  echo "pass"; else echo "fail"; fi
pass
dejan@ddeb:~$ if [ "${bios_version}" -eq "080015" ] ; then  echo "pass"; else echo "fail"; fi
pass
dejan@ddeb:~$

All are pass. Also, output of demidecode on my comp includes letter, so you might want to compare string, not integer for portability of your script.

iorih0304 · 08-09-2017, 02:04 AM

Sorry , I have another question
I write a shell script to check the MAC address as follow:

Code:

#!/bin/bash
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH

mac_address_sys=`ifconfig | grep 'HWaddr' | sed 's/^.*HWaddr //g'`
if [ "${mac_address_sys}" = "00:0c:29:b3:f7:54" ]; then
        echo "Check OK!"
else
        echo "Fail"
        echo "mac_address_sys is: "$mac_address_sys
fi

But the result is:

Code:

Fail
mac_address_sys is: 00:0c:29:b3:f7:54

I take it as a string, but it doesn't work.

Turbocapitalist · 08-09-2017, 02:23 AM

You are probably getting leading or trailing whitespace inside your string.

Try this instead:

Code:

mac_address_sys=$(ifconfig | sed '/HWaddr/!d; s/^.*HWaddr //; s/ *$//; q;')

The grep is not needed if you have sed.

"/HWaddr/!d" deletes all incoming lines without the string HWaddr

Those that get through are subjected to two substitutions.

And it goes without saying that what's left gets printed, since the -n option was not used.

Then sed quits after that so that in effect only the first interface is used.

iorih0304 · 08-09-2017, 03:01 AM

Thank you for your comment. It really explain why my code doesn't work.
I try your code, it can work.
Thanks a lot.

pan64 · 08-09-2017, 03:03 AM

you may try to use a delimiter:

Code:

echo "mac_address_sys is: '$mac_address_sys'"

and you will see if there was something strange before/after that address.

pan64 · 08-09-2017, 03:05 AM

Quote:

Originally Posted by Turbocapitalist

You are probably getting leading or trailing whitespace inside your string.

Try this instead:

Code:

mac_address_sys=$(ifconfig | sed '/HWaddr/!d; s/^.*HWaddr //; s/ *$//; q;')

The grep is not needed if you have sed.

awk is a bit more readable:

Code:

mac_address_sys=$(ifconfig | awk '/HWaddr/ {print $NF; exit}')

allend · 08-09-2017, 03:42 AM

Just for fun, a grep solution.

Code:

mac_address_sys=$(ifconfig | grep -o "..:..:..:..:..:..")

pan64 · 08-09-2017, 05:59 AM

and a shorter sed:

Code:

ifconfig | sed -n '/HWaddr/{s/.*ddr //;s/ *$//;p;q}'

allend · 08-09-2017, 07:31 AM

and a shorter grep

Code:

ifconfig | grep -oP "(?>..:){5}.."

iorih0304 · 08-09-2017, 10:10 PM

Quote:

Originally Posted by pan64

awk is a bit more readable:

Code:

mac_address_sys=$(ifconfig | awk '/HWaddr/ {print $NF; exit}')
ifconfig | sed -n '/HWaddr/{s/.*ddr //;s/ *$//;p;q}'

It looks more readable. Thanks.

Quote:

Originally Posted by allend

Just for fun, a grep solution.

Code:

mac_address_sys=$(ifconfig | grep -o "..:..:..:..:..:..")

In this case , the code is more simple to solve.