CODEWITHSUNDEEP
bashvariablescomparison
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Reputation: 3

[: missing `]' error while comparing variables with floating point numbers in a bash script

temp.txt is a file with a single line:

1.2034 3.2323 4.3121 5.1223

I have to do the following set of operations multiple times with different values so I have it all in a loop. Given below is the main issue I am facing and would appreciate some help solving.

v1=$(cut -d" " -f2 temp.txt);

v2=$(cut -d" " -f3 temp.txt);

v3=$(cut -d" " -f4 temp.txt);

v4=$(cut -d" " -f5 temp.txt);


#$v1, $v2, $v3, $v4 contain the above 4 values (1.2034, 3.2323, 4.3121, 5.1223). I have verified that. I want to compare their values, but when I do, I get an error because of incorrect syntax.

if [ "$v1" -gt "$v2" | bc ] && [ "$v3" -gt "$v4" | bc ]; then

    echo Yes

fi

I get this error:

line 6: [: missing `]'

File ] is unavailable.

Could someone please help me with my syntax? I have tried a few different things already and it didn't work. I have tried different combinations of brackets and spaces and both using bc and without bc.

Upvotes: 0

Views: 34

Answers (1)

chepner
chepner

Reputation: 531798

You want to construct a valid bc expression and pipe it to bc, capture the output, then compare that to the expected result.

if [[ $(echo "$v1 > $v2" | bc) == 1  &&  $(echo "$v3 > $v4" | bc) == 1 ]]; then
  echo Yes
fi

If bash could do floating-point arithmetic (or if your values were actually integers), you could do the comparisons directly in bash:

if [[ $v1 -gt $v2 && $v3 -gt $v4 ]]; then echo Yes; fi

or

if (( v1 > v2 && v3 > v4 )); then echo Yes; fi

A quicker way to populate your four variables is

read x1 v1 v2 v3 v4 x2 < temp.txt

(x1 and x2 are just variables whose value we don't really care about; the first field and any fields that might occur after the 5th thone.)

Upvotes: 1

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