Redirecting stdin throws ambigous redirect error

Question

I m trying to read in data either from a file or from the user's input to process it in a bash shell script. I m very new to it and I have this code working so far when the script accepts a file as an argument. When i try to create a new file that I can read the user's inputs and process it it throws an error : $datafilepath ambiguous redirect. I feel I m very close to it but I might be missing some good syntax. Can somebody push me in a right direction? Thanks!

#!/bin/bash
if [ "$#"  = "1" ]
then
    cat >>"$datafilepath"
elif  [ "$#" = "2" ]
then
    datafilepath=$2
fi

echo Average Median
while read myLine
do
    sum=0
    med=0
    for word in $myLine
        do
            sum=`expr $sum + $word`
            echo -e $word >> medfile
        done

sort < medfile >sorted
cat sorted | tr '\n' '\t' > rowfile
printf "%.0f\t%.0f\n" $(echo "scale=2; $sum/5" | bc ) $(cut -d' ' -f3 rowfile)
rm -f medfile
rm -f sorted
rm -f rowfile
done <$datafilepath

"ambiguous redirect" means `$datafilepath` is empty. (last line of your script) — jandob, Apr 17 '16 at 19:21
insert `set -x`on the 2nd line and run again the script. Bash will print debug output. — Jay jargot, Apr 17 '16 at 19:27
@jandob Thanks for the hint! How come is it empty if I use cat >> so it can take the user's input? — Mar Ina, Apr 17 '16 at 20:19
@Jayjargot Great tool! Thanks so much, great to see it debugging! — Mar Ina, Apr 17 '16 at 20:31

score 1 · Answer 1 · answered Apr 18 '16 at 05:31

#!/bin/bash
if [ "$#"  = "1" ]
then
    cat >>"$datafilepath"
elif  [ "$#" = "2" ]
then
    datafilepath=$2
fi

$datafilepath first appears in line #4, but it hasn't been initialized, so it's blank. The shell '>>' won't append unless there is a filename. There needs to be a line before that that sets $datafilepath to a default filename.

Line #2: the '1' should be a '0'. Line #5: the '2' should be a '1' Line #7: the '$2' should be a '$1'

This block has a needless file "sorted":

sort < medfile >sorted
cat sorted | tr '\n' '\t' > rowfile
printf "%.0f\t%.0f\n" $(echo "scale=2; $sum/5" | bc ) $(cut -d' ' -f3 rowfile)
rm -f medfile
rm -f sorted
rm -f rowfile

Suggested reduction:

sort medfile | tr '\n' '\t' > rowfile
printf "%.0f\t%.0f\n" $(echo "scale=2; $sum/5" | bc ) $(cut -d' ' -f3 rowfile)
rm -f medfile rowfile

Redirecting stdin throws ambigous redirect error

1 Answers1