bash error: 2: integer expression expected - linux

Question

I have a problem with a simple bash script..
#!/bin/bash
libc_main_ver=$(dpkg -l |grep libc6 |awk '{print$3}' |awk -F .
'{print$1}'|xargs -n 1)
if [ "$libc_main_ver" -eq 2 ] ;then
echo ok
else
echo nope
fi
exit 0
When i try execute the script it gives me the error:
2: integer expression expected
What's the problem?
dpkg -l |grep libc6 |awk '{print$3}' |awk -F . '{print$1}'|xargs -n 1
This prints only 2 not other values.
Some suggestions?

Answer 1

Insert
echo "<$libc_main_ver>"
after the first line and the error will be obvious. Very likely there's a space or newline in there somewhere which you shouldn't numerically compare with 2.
Very esoteric: the problem could be the literal in -eq 2 as well. If it is followed by a carriage return character, I can somewhat reproduce your error message:
$ test "2" -eq 2^R
bash: test: 2: integer expression expected
where ^R is a literal carriage return entered with CTRL-V CTRL-R. To verify or exclude this, run od -bc nameofyourscript

Answer 2

What if you tried this:
#!/bin/bash
libc_main_vers=$(dpkg -l | grep libc6 | awk '{ print $3 }' | awk -F . '{ print $1 }')
for ver in ${libc_main_vers}; do
if (( ver == 2 )); then
echo ok
else
echo nope
fi
done
exit 0

Answer 3

Here is another version:
#!/bin/bash
libc_full=$(dpkg -l | grep libc6 | head -n 1 | awk '{ print $3 }')
libc_main=$(echo ${libc_full} | grep -o "^[0-9]*")
libc_update=$(echo ${libc_full} | grep -o "[0-9]*$")
if (( libc_main == 2 )); then
echo "Main version is OK"
if (( libc_update >= 7 )); then
echo "Update version is OK"
exit 0
fi
fi
exit 1

Answer 4

It's unclear whether you require all the packages you list to have a major version number 2, or are just verifying that at least one of them does.
Anyway, if we start with the observation that grep foo | awk { print $1 } can usually be refactored into a single Awk script awk '/foo/ { print $1 }' we can already simplify your script; but it sometimes makes sense to refactor basically all of it into Awk. Perhaps like this:
dpkg -l 'libc6*' | awk '$3 !~ /^2\./ { exit 1 }' && echo ok || echo nope
If you are satisfied with just one package meeting the condition, change to something like
dpkg -l 'libc6*' | awk '$3 ~ /^2\./ { exit 0 } END { exit 1 }' && echo ok || echo nope
As always, foo && success || failure is a shorthand for
if foo; then
success
else
failure
fi
where the longhand probably makes sense if your real script needs to do something moderately more complex than just echo a value.
Do note that the output from dpkg -l is not necessarily suitable for scripts. Maybe use dpkg-query -f '${Version}\n' -W 'libc6' instead for robustness.