Shell script linux command not found for uname -a

hallomoto · 04-16-2019, 11:47 AM

check.sh: line 8: Linux: command not found

When I run the script, it tells me command not found even though the first if statement is fine.

-rwxrwxrwx 1 root root 3706 Apr 16 11:36 check.sh

Code:

function usage {
    echo "$USAGE";
} # end function: usage

# Get OS Release version
if $(uname -a | grep el6); then
    OS_RELEASE_VERS="6"
elif $(uname -a | grep el7); then
    OS_RELEASE_VERS="7"
else
    OS_RELEASE_VERS="0"
fi

freemedia2018 · 04-16-2019, 12:15 PM

Try it without the $( )

Code:

if uname -a | grep el6 ; then
    OS_RELEASE_VERS="6"
elif uname -a | grep el7 ; then
    OS_RELEASE_VERS="7"
else

MadeInGermany · 04-16-2019, 04:32 PM

A smart alternative is a case-esac

Code:

case $(uname -a) in
( *el6* ) OS_RELEASE_VERS="6"
;;
( *el7* ) OS_RELEASE_VERS="7"
;;
( * ) OS_RELEASE_VERS="0"
esac

Here you need the $( ) because the case needs a string.
The $( ) runs the enclosed shell code and is then substituted by its output.

berndbausch · 04-16-2019, 08:02 PM

While two solutions were given, you may wonder why the original code didn't work.

Code:

if $(uname -a | grep el7); then
...

does the following:

Run the command uname -a | grep el7
Take the output of step 1 and substitute $(...) with it
Execute the if

The output in step 2 looks like this: Linux MACHINENAME KERNELVERSION .... Therefore, the if condition in step 3 becomes

Code:

if Linux MACHINENAME KERNELVERSION ...

which results in a syntax error, since there is no command named Linux.