Unix script giving error trying to assign variable?

Question

I'm extremely new to Unix, and this is driving me crazy. I am getting this error:

./lines: line 21: [[: grep -c *.* $3: syntax error: operand expected
(error toke                                           n is ".* $3")
./lines: line 26: [[: grep -c *.* $3: syntax error: operand expected
(error toke n is ".* $3")

When running this script:

#!/bin/bash
#lines <start> <finish> <file> prints lines start-finish of file

if [[ $# != 3 ]]
then    echo "Command format: lines <starting line> <end line> <filename>"
    exit
fi

tLines='grep -c *.* $3'
start=$1
finish=$2

if [[ $finish -lt $start ]]
    then echo "$finish is less than $start. I'll go ahead and reverse those for you."
    start=$2
    finish=$1
fi

start=$((finish-start+1))

if [[ $tLines -lt $start ]] 
    then echo "$3 is only $tLines lines - that's less than $start"
    exit
fi

if [[ $tLines -lt $finish ]]
    then echo "3 is only $tLines line - that's less than $finish"
    exit
fi
head -$finish $3 | tail -$start
exit

I have no idea what those errors mean and searching them online have not given me much insight. I appreciate any help!

how are you invoking the script?

sehe
– sehe

2013-10-06 23:33:39 +00:00
Commented Oct 6, 2013 at 23:33 — sehe
– sehe, Commented Oct 6, 2013 at 23:33

C2H5OH · Accepted Answer · 2013-10-06 23:47:52Z

2

Seems like you wanted to use command substitution here:

tLines='grep -c *.* $3'

But you used the wrong quotes. The correct ones are the legacy backticks:

tLines=`grep -c *.* $3`

Or the newer form:

tLines=$(grep -c *.* $3)

edited Oct 6, 2013 at 23:47

answered Oct 6, 2013 at 23:41

C2H5OH

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