UNIX for Dummies Questions & Answers

#!/bin/bash
#

# check that something was piped to the script
# by reading the actual pipe descriptor
if [ $(readlink /proc/$$/fd/0 | grep -c "^pipe:") == 1 ]
then
    # store the value that was piped to the script
    input=$(cat /proc/$$/fd/0)

    # extract the bytes and remove the commas
    sz=$(echo $input | awk '{gsub(/,/,"",$3); print $3}')

    # convert the bytes to gigabytes and compare if greater
    # than 2GBs
    getsize=$(echo "scale=0;${sz}/1024/1024/1024"|bc)
    if [ $getsize -gt 2 ]
    then
        echo "Current size is greater than the 2GB threshold."
    else
        echo "Current size is within range."
    fi
else
    echo "Nothing on the pipeline."
    exit 1
fi

# done
exit 0

echo "9 Dir(s) 6,611,517,440 bytes free" | ./chkSize.sh
Current size is greater than the 2GB threshold.