Hello. I am trying to write a simple script (one of my attempts is below) to multiply the contents of a file by -1. I have a folder filled with many files and these txt files are each a single column of numbers and I just need to flip the signal to negative numbers and save out the inverted version of each. I am unable to write a cygwin script to do it properly. Any assistance is appreciated.
for file in *txt
do
$file | bc -q
$file *-1 > $file-inverted.txt
done
echo "files inverted"
You can experiment a little with how you want your data inside double-quotes, but you need to make sure the unix environment does not attempt to interpret your text. Think that a -1 is very similar to an option in appearance. [For example, the command ls -1 would list files in one column.]
> echo "5" "*" "-1" | bc
-5
> echo "-55" "*" "-1" | bc
55
Thank you for the response. I have experimented with the quotes and it still isn't working properly. It seems to be having trouble with the use of $file in conjunction with bc.
I am fairly new to unix scripts, so forgive me if I'm missing something obvious.
An alternative with awk:
for file in *txt
do
awk '{$0*=-1}1' ${file} > ${file}-inverted.txt
done
echo "files inverted"
input file
> cat file161
10
-13
1962
-1991
script
> cat play161.sh
#! /usr/bin/bash
while read NUM_IN
do
INITIAL=`echo ${NUM_IN}`
NEW_VAL=`echo "${NUM_IN} * -1" | bc`
echo ${INITIAL} " and " ${NEW_VAL}
done <file161
script execution
> play161.sh
10 and -10
-13 and 13
1962 and -1962
-1991 and 1991
the awk alternative works great. thanks for the tip, I've never used awk for math before.