Shell Script troubles

DemonWav · 01-03-2012, 09:58 PM

First off I want to start off saying that I am working on this script for an Android phone, so the commands are generally limited to busybox. If busybox can't do it, then neither can I. This is the entire script I am working on:

Code:

#!/sbin/sh

if [ -e /dev/block/mtdblock0 ] ; then
	if [ -d /data ] ; then
		/tmp/busybox mount -t ext4 /dev/block/mmcblk0p2 /data
	else
		/tmp/busybox mkdir mkdir /data
		/tmp/busybox mount -t ext4 /dev/block/mmcblk0p2 /data
	fi
	
	if [ -h /data/data/ ] ; then
		/tmp/busybox touch /tmp/nofix
	else
		if [ -d /datadata ] ; then
			/tmp/busybox mount -t yaffs2 /dev/block/mtdblock6 /datadata
		else
			/tmp/busybox mkdir /datadata
			/tmp/busybox mount -t yaffs2 /dev/block/mtdblock6 /datadata
		fi
		/tmp/busybox rm -rf /datadata/*
		FREE_SPACE=$(/tmp/busybox df -h | /tmp/busybox awk '$1 == "/dev/block/mtdblock6" {print $3}') ; USED_SPACE=$(/tmp/busybox du -sh /data/data/ | /tmp/busybox awk '{print $1}')
		NEW_TERM=$(echo $FREE_SPACE $USED_SPACE | /tmp/busybox awk '{print $1 $2}')
		FREE_SPACE=$(echo $NEW_TERM | /tmp/busybox awk '{print $1}') ; USED_SPACE=$(echo $NEW_TERM | /tmp/busybox awk '{print $2}')
		if [ $FREE_SPACE -gt $USED_SPACE ] ; then
			/tmp/busybox touch /tmp/revert_pass
		else
			/tmp/busybox touch /tmp/revert_fail
		fi
	fi
else
	exit 1
fi

All goes well and good, until I get to line 22:

Code:

NEW_TERM=$(echo $FREE_SPACE $USED_SPACE | /tmp/busybox awk '{print $1 $2}')

Basically my problem is I need two integers to do the test in line 24:

Code:

if [ $FREE_SPACE -gt $USED_SPACE ] ; then

and the output from the command on line 21:

Code:

FREE_SPACE=$(/tmp/busybox df -h | /tmp/busybox awk '$1 == "/dev/block/mtdblock6" {print $3}') ; USED_SPACE=$(/tmp/busybox du -sh /data/data/ | /tmp/busybox awk '{print $1}')

is something like 132.5M for FREE_SPACE and 129.7M for USED_SPACE (I basically just made up those numbers, but they are numbers like that, 3 digits before the decimal, a digit after the decimal, and an M). What I am attempting to do with line 22 is try to maybe do 3 backspaces, if you will, on each of the two results. so 132.5M becomes 132 and 129.7M becomes 129. I don't need to know the decimal, it is really unimportant for my purposes. If I can accomplish that then I will be set for the rest of the script, but I really have no idea how to do that (or if its possible at all).

Nominal Animal · 01-03-2012, 11:33 PM

Quote:

Originally Posted by DemonWav

Code:

FREE_SPACE=$(/tmp/busybox df -h | /tmp/busybox awk '$1 == "/dev/block/mtdblock6" {print $3}')
USED_SPACE=$(/tmp/busybox du -sh /data/data/ | /tmp/busybox awk '{print $1}')

Why not use df -k and du -sk instead? That should give the sizes in integer kilobytes.

You could also guard against integer overflow, using

Code:

FREE_SPACE=$(/tmp/busybox df -k | /tmp/busybox awk '$1 == "/dev/block/mtdblock6" {print int($3/1024) }')
USED_SPACE=$(/tmp/busybox du -sk /data/data/ | /tmp/busybox awk '{print int($1/1024) }')

in which case they're both in megabytes (MiB, or units of 1024*1024=1048576 bytes). (The awk expression also makes sure they're integers; no decimals. You may wish to use int($1/1024+512) and int($3/1024+512) if you want correct rounding; the above rounds towards zero.)

DemonWav · 01-04-2012, 12:49 AM

Dude, you're awesome! Thanks! Yeah, I'm kinda new at this (well, new at making these more complex scripts) and I had never heard of awk before until I started looking around for some way to accomplish my goal. Or df or du, so I wasn't all to sure with what I could do with them. But what you suggested worked perfectly, thanks for the help!