Question

I am trying to check if a value I read from a text file is zero:

[[ $(echo $line | cut -d" " -f5) -gt 0 ]] && [[ $(echo $line | cut -d" " -f7 | bc -l) -eq 0 ]]

With the first condition there is no problem because f5 are integers. The problem comes form the second condition. I receive this error message:

[[: 1.235: syntax error: invalid arithmetic operator (error token is ".235")

I have tried several suggestions I found in different forums such as using echo $line | cut -d" " -f7 | bc -l with and without double quotes, etc. However, the error persist. f7 is a positive number and is given with 3 decimal places. Removing decimals or approximating is not an option because I need the result to be exactly zero (0.000).

Answer 1

Use a string comparison instead. Replace:

-eq 0

with:

= '0.000'

---

TZ:

Script section from comment:

for clus in $(ls *.cluster) ; do
    while read line ; do
        if [[ $(echo $line | cut -d" " -f11) -gt 0 ]] && [[ "$(echo $line | cut -d" " -f15 | bc -l)" = '0.000' ]] ; then
            cat $(echo $line | cut -d" " -f6).pdb >> test/$(echo $line | cut -d" " -f2)_pisa.pdb
        fi
    done < $clus
done

My pseudo-Python interpretation:

for clus in *.cluster:
    for line in clus:
        fields = line.split(' ')
        # field numbers are counting from 1 as in cut
        if int(field 11) > 0 and str(field 15) == '0.000':
            fin_name = (field 6) + '.pdb'
            fout_name = (field 2) + '_pisa.pdb'
            cat fin_name >> fout_name

Is that what you intended?