Pulling variables from file with bash

SJD · 07-23-2007, 09:07 AM

Hi all,

I have a line that I have grep on which contains a number of variables and I would like to remove those numbers as variables. The line is:

XXX heads, YYY cylinders, ZZZ sectors

where XXX, YYY and ZZZ are numerical values that I need. The numbers could be any length so I cannot output a set number of characters. Is it possible to output these numbers as variables using bash? I apologise if this is a basic question, but I have looked on the internet, but I haven't been able to find anything to help me.

Thanks,

Steve

Matir · 07-23-2007, 09:17 AM

You could use awk to split out the fields, like this:

Code:

LINE="123 heads, 456 cylinders, 789 sectors"
HEADS=`echo $LINE | awk '{print $1}'`
echo "HEADS=$HEADS"
CYLINDERS=`echo $LINE | awk '{print $3}'`
echo "CYLINDERS=$CYLINDERS"
...

slakmagik · 07-23-2007, 10:20 AM

Not especially important, but maybe worth mentioning: to cut three awk invocations to one, you could use something like

Code:

LINE="123 heads, 456 cylinders, 789 sectors"
export $(echo $LINE | awk '{ print "HEADS="$1 " CYLINDERS="$3 " SECTORS="$5 }')

-- I'm having a brain-damaged day. It occurred to me to go entirely awk-less, but there's got to be a better way than this:

Code:

LINE="123 heads, 456 cylinders, 789 sectors"
read HEADS foo CYLINDERS bar SECTORS baz < <(echo $LINE)
echo "HEADS=$HEADS"
echo "CYLINDERS=$CYLINDERS"
echo "SECTORS=$SECTORS"

or this

Code:

LINE="123 heads, 456 cylinders, 789 sectors"
read -a DISKGEOM < <(echo $LINE)
echo "HEADS=${DISKGEOM[0]}"
echo "CYLINDERS=${DISKGEOM[2]}"
echo "SECTORS=${DISKGEOM[4]}"

but whatever. *sigh*

SeRGeiSarov · 07-23-2007, 12:58 PM

Quote:

Not especially important, but maybe worth mentioning: to cut three awk invocations to one, you could use something like

Code:

LINE="123 heads, 456 cylinders, 789 sectors"
export $(echo $LINE | awk '{ print "HEADS="$1 " CYLINDERS="$3 " SECTORS="$5 }')

It is effective example.
How to do example without EXPORT?

unSpawn · 07-23-2007, 01:28 PM

I like the 'read' way, but here's one w/o any external binaries. Not *that* portable but oh well..

Code:

LINE="123 heads, 456 cylinders, 789 sectors"
LINE=${LINE//heads,}; LINE=${LINE//cylinders,}; LINE=${LINE//sectors}
LINE=(${LINE})
export `eval echo HEADS=${LINE[0]}`
export `eval echo CYLINDERS=${LINE[1]}`
export `eval echo SECTORS=${LINE[2]}`

slakmagik · 07-23-2007, 03:03 PM

Quote:

Originally Posted by SeRGeiSarov

It is effective example.
How to do example without EXPORT?

One way would be to s/export/eval/ - as if we need more ways.