I am trying to do a simple comparison to check if a line is empty using bash:
line=$(cat test.txt | grep mum )
if [ "$line" -eq "" ]
then
echo "mum is not there"
fi
But it is not working, it says: [: too many arguments
Thanks a lot for your help!
You could also use the $? variable that is set to the return status of the command. So you'd have:
line=$(grep mum test.txt)
if [ $? -eq 1 ]
then
echo "mum is not there"
fi
For the grep command if there are any matches $? is set to 0 (exited cleanly) and if there are no matches $? is 1.
if grep -q mum test.txt; then ...
if [ ${line:-null} = null ]; then
echo "line is empty"
fi
or
if [ -z "${line}" ]; then
echo "line is empty"
fi
[[ (You should always use [[ when using bash). In the case of -z it works, but for any other test, it will cause an error if the variable is empty.
line="foo -o bar"; if [ -z $line ]; then echo "line is empty"; else echo "line is not empty"; fiThe classical sh answer that will also work in bash is
if [ x"$line" = x ]
then
echo "empty"
fi
Your problem could also be that you are using '-eq' which is for arithmetic comparison.
grep "mum" file || echo "empty"
if line=$(grep -s -m 1 -e mum file.txt)
then
echo "Found line $line"
else
echo 'Nothing found or error occurred'
fi
I think the clearest solution is using regex:
if [[ "$line" =~ ^$ ]]; then
echo "line empty"
else
echo "line not empty"
fi
If you want to use PHP with this,
$path_to_file='path/to/your/file';
$line = trim(shell_exec("grep 'mum' $path_to_file |wc -l"));
if($line==1){
echo 'mum is not here';
}
else{
echo 'mum is here';
}
