-Gt: Unary Operator Expected Shell Script
Getting This Error After the Upgrade Packages in Ubuntu. #! /Bin/Bash Used=$(Df -H | Grep 'Rootfs' | Cut -D "G" -F 4 | Cut -D "%" -F 1) Limit=90 If [ $Used -Gt...
Getting this error after the upgrade packages in ubuntu.
#!/bin/bash
used=$(df -H | grep 'rootfs' | cut -d "G" -f 4 | cut -d "%" -f 1)
limit=90
if [ $used -gt $limit ]; then Or [ "$used" -gt "$limit" ] Or [ "$used" -ge 90 ]
#delete file and mail command;
fi
Error
[: -gt: unary operator expected
1 Answer
The variable used is empty, leading to the error message regarding unary operator. Possible reason could be there is no rootfs in df -H output i.e. in your system.
$ foo=
$ [ $foo -gt 10 ] && echo OK
bash: [: -gt: unary operator expected
You have also some other issues in your script, the OR logic should be put as:
[ "$foo" -gt "$bar" ] || [ "$foo" -ge 90 ]
Also better use the shell keywod [[ instead of test ([) command to avoid many pitfalls:
[[ "$foo" -gt "$bar" ]] || [[ "$foo" -ge 90 ]]
For arithmetic comparisons, you can also use (( and regular arithmetic operators:
(( "$foo" > "$bar" )) || (( "$foo" >= 90 ))
You don't even need to put $ in-front of the variable name:
(( foo > bar )) || (( foo >= 90 ))
Sarah Jenkins is a veteran tech journalist with over 12 years of experience covering artificial intelligence, mobile innovations, and digital ethics. Her insights have appeared in leading technology publications worldwide.
