Pause a process before disk is full

Question

Certain processes (like git gc --aggressive ) take a long time to run, take up lots of disk space, and die if I run out of disk space. So I'd like to pause them if the disk will run out of space soon, so I have time to free up some memory. How can I do this?

Answer 1

Here is an initial solution I came up with. Tested with Mac OS X. Suggestions welcome!

#!/bin/bash
FILESYSTEM="/dev/disk1"
DF=/usr/local/opt/coreutils/libexec/gnubin/df
OSASCRIPT=/usr/bin/osascript

if ! [[ -x $DF ]]; then echo "Error: $DF isn't executable."; exit 1; fi

PID=$1
STOPAT=$2

# Verify input
if [[ -n ${PID//[0-9]/} ]]; then echo "Error: The first parameter should be an integer"; exit 1; fi
if [[ -n ${STOPAT//[0-9]/} ]]; then echo "Error: The second parameter should be an integer"; exit 1; fi

RED='\033[0;31m'; PURPLE='\033[0;35m'; BLUE='\033[0;36m'
NC='\033[0m' # No Color

echo -e "Will pause the following process when there are ${PURPLE}$STOPAT${NC} bytes left on ${PURPLE}$FILESYSTEM${NC}"

PROCESS=`ps -p $PID | grep $PID`
echo -e "${BLUE}$PROCESS${NC}"

# Check every second to see if FILESYSTEM has more than STOPAT bytes left.
while true; do
    left=`$DF | grep -m 1 $FILESYSTEM | tr -s ' ' | cut -d" " -f4`
    echo -ne "$left bytes left\r";
    if [[ $left -lt $STOPAT ]]; then
        MSG="pausing process...$PID";
        echo $MSG;
        if [[ -x $OSASCRIPT ]]; then
             $OSASCRIPT -e "display notification \"$MSG\""
        fi
        kill -TSTP $PID
        break
    fi
    sleep 1s
done

You'll need to change DF to match your df . (I didn't call df directly because on my system that is aliased to df -h .)