Setting variables in shell script by running commands

Question

>cat /tmp/list1
john
jack

>cat /tmp/list2
smith
taylor

It is guaranteed that list1 and list2 will have equal number of lines.

    f(){
        i=1
        while read line
          do
        var1 = `sed -n '$ip' /tmp/list1`
        var2 = `sed -n '$ip' /tmp/list2`
        echo $i,$var1,$var2
        i=`expr $i+1`
            echo $i,$var1,$var2
          done < $INFILE
    }

So output of f() should be:

1,john,smith
2,jack,taylor

But getting

1,p,p
1+1,p,p

If i replace following:

var1 = `sed -n '$ip' /tmp/list1`
var2 = `sed -n '$ip' /tmp/list2`

with this:

var1=`head -$i /tmp/vip_list|tail -1`
var2=`head -$i /tmp/lb_list|tail -1`

Then output:

1,john,smith
1,john,smith

Most shells of the Borne family also accept the notation i=$(( $i + 1 )) for calculations and $(command) for execution. I find this much nicer... besides you can nest them in ways the execution quotes do not allow or makes things clearer to most readers. x="$( foo "$bar" $(( $i + 1 )) )"; — Gilbert
– Gilbert, Commented Sep 16, 2012 at 15:50

P.P · Accepted Answer · 2012-09-16 15:37:34Z

2

If you can use paste and awk command, you can achieve the same with a one-liner:

paste -d, /tmp/list1 /tmp/list2 | awk '{print NR "," $0}'

Replace the while script with this line :)

answered Sep 16, 2012 at 15:37

P.P

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Comments

xception · Accepted Answer · 2012-09-16 22:00:54Z

2

the $ip is the problem there making ip the name of the variable, you should use ${i}p instead letting the shell know that the variable is i not ip, your code should look like

var1=`sed -n "${i}p" /tmp/list1`

var2=`sed -n "${i}p" /tmp/list2`

edited Sep 16, 2012 at 22:00

answered Sep 16, 2012 at 15:36

xception

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2 Comments

Jens Over a year ago

How is this supposed to work with the spaces around the = and the substitution-inhibiting single quotes around $i?

xception Over a year ago

edited with double quotes and no spaces, I'm new here and find it hard to type right in this thing, first 3 tries everything was in a single line

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