Error near unexpected token `(' but then permission denied

I am trying to run this nagios plugin:

sudo /usr/lib64/nagios/plugins/check_generic.pl -n "slab_mem" -e "SLAB=$$(cat /proc/meminfo | egrep "Slab:" | awk '{print $$2;}'); MEMTOTAL=$$(cat /proc/meminfo | egrep "MemTotal:" | awk '{print $2;}'); awk "BEGIN {print 100*$$SLAB/$$MEMTOTAL}"" -w '>50' -c '>80' -p "slab_mem"

It shows this error:

sh: -c: line 0: syntax error near unexpected token `('
sh: -c: line 0: `SLAB=76876(cat /proc/meminfo | egrep "Slab:" | awk '{print 768762;}'); MEMTOTAL=76876(cat /proc/meminfo | egrep "MemTotal:" | awk '{print ;}'); awk BEGIN 1>/var/tmp/check_generic/check_generic_stdout_77319.64001 2>/var/tmp/check_generic/check_generic_stderr_77319.23364'
slab_mem UNKNOWN - result:RC1 output: match:RC!=OK |slab_mem=;50.000000;80.000000;;

I found that escaping ( and ) could make it work, but it doesnt, then it gives this error:

-bash-4.1$ /usr/lib64/nagios/plugins/check_generic.pl -n "slab_mem" -e "SLAB=$$\(cat /proc/meminfo | egrep "Slab:" | awk '{print $$2;}'\); MEMTOTAL=$$\(cat /proc/meminfo | egrep "MemTotal:" | awk '{print $2;}'\); awk "BEGIN {print 100*$$SLAB/$$MEMTOTAL}"" -w '>50' -c '>80' -p "slab_mem"
sh: /proc/meminfo: Permission denied
awk: {print 749962;})
awk:                ^ syntax error
sh: /proc/meminfo: Permission denied
awk: {print ;})
awk:          ^ syntax error

The only information I found while trying to read /proc/meminfo is because some people tried to execute it (instead of reading with cat) but this is not the case.

EDIT: Trying to escape $$: Command:

-bash-4.1$ /usr/lib64/nagios/plugins/check_generic.pl -n "slab_mem" -e "SLAB=\$\$\(cat /proc/meminfo | egrep "Slab:" | awk '(print $$2'\) MEMTOTAL=\$\$\(cat /proc/meminfo | egrep "MemTotal:" | awk '{print $2;}'\); awk "BEGIN {print 100*\$\$SLAB/\$\$MEMTOTAL}"" -w '>50' -c '>80' -p "slab_mem"

Result:

sh: /proc/meminfo: Permission denied
awk: {print ;})
awk:          ^ syntax error
awk: (print 499542)
awk:  ^ syntax error
awk: cmd. line:1: (print 499542)
awk: cmd. line:1:               ^ unexpected newline or end of string
slab_mem UNKNOWN - result:RC1 output: match:RC!=OK  [awk: cmd. line:1: BEGIN blocks must have an action part]|slab_mem=;50.000000;80.000000;;

SLAB=76876(cat /proc/meminfo | egrep "Slab:" | awk '{print 768762;}')

the shell parses that into these words

SLAB="76876(cat" /proc/meminfo | egrep "Slab:" | awk '{print 768762;}')
^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^ .......................................^

Where the "(cat" characters are part of the value for the SLAB temporary environment variable.

Then, the shell is attempting to call /proc/meminfo as a command.

That leaves an unpaired closing parenthesis causing the awk syntax error

I'm unclear what the purpose of SLAB=$$ and the (cat ...) is. Are you trying to set the SLAB variable to hold a value that concatenates the pid and the result of parenthesized code?

My solution: I'd build the nagios -e command in pieces:

nagios_cmd=""
for var in Slab MemTotal; do
    nagios_cmd+=$(printf '%s="${$}$(awk '\''/%s:/ {print $2}'\'' /proc/meminfo)"; ' $var $var)
done

nagios_cmd+='awk -v s="$Slab" -v m="$MemTotal" '\''BEGIN {print 100*s/m}'\'

declare -p nagios_cmd

This outputs

declare -- nagios_cmd="Slab=\"\${\$}\$(awk '/Slab:/ {print \$2}' /proc/meminfo)\"; MemTotal=\"\${\$}\$(awk '/MemTotal:/ {print \$2}' /proc/meminfo)\"; awk -v s=\"\$Slab\" -v m=\"\$MemTotal\" 'BEGIN {print 100*s/m}'"

which shows you the shell will protect all the chacters that need protecting.

Then you invoke the nagios check like:

/usr/lib64/nagios/plugins/check_generic.pl -n "slab_mem" -e "$nagios_cmd" -w '>50' -c '>80' -p "slab_mem"
# ..........................................................^^^^^^^^^^^^^

That can be written as a single awk command without needing the temporary shell variables:

nagios_cmd='awk -F":" -v pid="$$" '\''
    $1 == "Slab" {s = pid $2}
    $1 == "MemTotal" {m = pid $2}
    END {print 100*s/m}
'\'' /proc/meminfo'

Or, to help with the quoting hell, a here-document:

nagios_cmd=$(cat <<'END_CMD'
    awk -F":" -v pid="$$" '
        $1 == "Slab" {s = pid $2}
        $1 == "MemTotal" {m = pid $2}
        END {print 100*s/m}
    ' /proc/meminfo
END_CMD
)