If shell escaping of the command is problematic, you can write the command to a file first: batch <somefile Or read it: read -re && echo "$REPLY" | batch Or, if your shell supports it, you can eliminate echo: read -re && batch <<<$REPLY ("man batch" lists 1.5 for me, but I don't know how widely it differs.)

Show the current load of the CPU as a percentage. Read the load from /proc/loadavg and convert it using sed: Strip everything after the first whitespace: sed -e 's/ .*//' Delete the decimal point: sed -e 's/\.//' Remove leading zeroes: sed -e 's/^0*//' Show Sample Output

[ 2000 -ge "$(free -m | awk '/buffers.cache:/ {print $4}')" ] returns true if less than 2000 MB of RAM are available, so adjust this number to your needs. [ $(echo "$(uptime | awk '{print $10}' | sed -e 's/,$//' -e 's/,/./') >= $(grep -c ^processor /proc/cpuinfo)" | bc) -eq 1 ] returns true if the current machine load is at least equal to the number of CPUs. If either of the tests returns true we wait 10 seconds and check again. If both tests return false, i.e. 2GB are available and machine load falls below number of CPUs, we start our command and save it's output in a text file. The ( ( ... ) & ) construct lets the command run in background even if we log out. See http://www.commandlinefu.com/commands/view/3115/ .

I run this via crontab every one minute on my machine occasionally to see if a process is eating up my system's resources.