check leading and trailing white space from a variable and fail the script

dilip_d21 · 12-10-2021, 09:11 AM

Hi All ,

I was trying this for some time and can one one please help , consider variable called release has some value called 1.0.11 , i want to check that variable if it has any leading or trailing space and in case if it has any space then the script should fail , how can i achieve this ??

I tried the below code but this does not work

release=1.0.11

```if [ release=${release// } ]; then
echo "release version has trailing or leading whitespaces"
exit 1
else
echo "release version value is fine"
fi```

Any help much appreciated

pan64 · 12-10-2021, 09:27 AM

if [ $release=${release// } ]; then

michaelk · 12-10-2021, 09:46 AM

Almost...

Code:

if [[ $release != ${release// } ]]; then
  echo "release version has trailing or leading whitespaces"
  exit 1
else
  echo "release version value is fine"
fi

pan64 · 12-10-2021, 09:48 AM

you are right. Anyway, shellcheck is our friend.

dilip_d21 · 12-10-2021, 10:06 AM

Thanks guys , i checked the above code but unfortunately i got the wrong result, the release version is a input parameter text box which will be feed manually , their is lot of chances people leave spaces in front or after enter the version but the code is not picking up the space but not sure why and i got the result as

as release version value is fine when actually i gave release= 1.0.100 and release=1.0.100 (here a space after 100 )

but in linux release= 1.0.100 is not accepted

can this be solved in anyways ??

thanks

shruggy · 12-10-2021, 11:12 AM

Quote:

Originally Posted by dilip_d21

the release version is a input parameter text box which will be feed manually

By default, the read shell builtin will strip leading and trailing white spaces (unless you change $IFS to a custom value).

Code:

read -r release <<<"$1"

Quote:

Originally Posted by dilip_d21

but in linux release= 1.0.100 is not accepted

Probably a quoting problem. But saving the value with leading/trailing spaces in it is not needed at all, see above.

michaelk · 12-10-2021, 04:11 PM

To assign variables with spaces they must be quoted which as posted should not be needed since your using a read statement

release=" 10.0.100 "

dilip_d21 · 12-13-2021, 03:40 AM

Hi shruggy, Thanks for the reply

But my requirement is not to trim the space , my requirement is to check for leading and trailing white spaces and if any space is found then the script should fail.

Is this can be handled by any other way ??

Thanks

shruggy · 12-13-2021, 03:53 AM

Then, as michaelk wrote above, quote the value.

michaelk · 12-13-2021, 05:51 AM

What generates the text box? zenity, dialog?

dilip_d21 · 12-13-2021, 06:10 AM

this code worked for me guys..

echo "$(release)"

case "$(release)" in
*[[:space:]]*)
echo "Release version has trailing or leading whitespaces" >&2
exit 1
;;
esac

Thanks all for the support,cheers

shruggy · 12-13-2021, 06:16 AM

Quote:

Originally Posted by dilip_d21

echo "$(release)"

You mean "${release}", right?

Quote:

Originally Posted by dilip_d21

case "$(release)" in

The case variable is an uncommon example of a variable that may be left unquoted

Code:

case $release in

should work the same.

Quote:

Originally Posted by dilip_d21

*[[:space:]]*)

would of course catch any internal spaces as well.

syg00 · 12-13-2021, 06:24 AM

This is all so arcane - is insisting on shell the right solution ?.

dilip_d21 · 12-13-2021, 06:27 AM

I mean only $(release) , this is a variable from azure which has the value(parameter defined across which can be used across the stage ), thanks

shruggy · 12-13-2021, 06:41 AM

Microsoft Azure is a very unusual platform for Linux. You should have mentioned it from the start.