Redis: who is eating my field when piping llen results through awk?

Question

Redis: 2.0.4, 2.4.1, ... I'm going to write a Nagios plugin to check the length of a list. Here's my script: ``` #!/bin/sh help() { echo "Usage: $0 -w -c " } case "$1" in --help) help exit ;; esac if [ $# -eq 0 ]; then help exit 3 fi if [ $# -ne "7" ]; then help exit 4 fi if [ $4 !="-w" -o $6 !="-c" ]; then help exit 5 fi REDIS_CLI="/usr/local/redis/bin/redis-cli" LLEN=`$REDIS_CLI -h $1 -p $2 llen $3 | awk '{ print $2 }'` if [ $LLEN -lt $5 ]; then echo "$3.llen:$2 OK - $LLEN | $3.llen:$2=$LLEN;$5;$7" exit 0 elif [ $LLEN -ge $5 -a $LLEN -lt $7 ]; then echo "$3.llen:$2 WARNING - $LLEN | $3.llen:$2=$LLEN;$5;$7" exit 1 elif [ $LLEN -ge "$7" ]; then echo "$3.llen:$2 CRITICAL - $LLEN | $3.llen:$2=$LLEN;$5;$7" exit 2 fi ``` but I got the following error when running `/usr/lib64/nagios/plugins/redis_llen.sh 192.168.5.201 2468 -w 90000 -c 100000`: ``` /usr/lib64/nagios/plugins/redis_llen.sh: line 31: [: -lt: unary operator expected /usr/lib64/nagios/plug…

Accepted Answer

What you're experiencing is `redis-cli` selecting different outputs depending on what `STDOUT` is. If `STDOUT` is a TTY, `redis-cli` will output using it's "standard" formatting. Otherwise, the "raw" formatting is the default:

```
--raw            Use raw formatting for replies (default when STDOUT is not a tty)
```

As you see from the help, or the above, you can specify `--raw` to always have it output the "raw" format (without type qualifiers, etc). What I found out digging through the source for this, is that there is also a CSV mode, using `redis-cli --csv`.

Edit: To force the "standard" output, even when `STDOUT` is not a TTY, you can set the environment variable `FAKETTY`:

```
FAKETTY=1 redis-cli llen some_list | awk '{ print $2 }'
```

Or

```
redis-cli --raw llen some_list | awk '{ print $1 }'
```

Redis: who is eating my field when piping llen results through awk?

Solution

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