bash/awk/unix detect changes in lines of csv files - linux

Question

I have a timestamp in this format:
(normal_file.csv)
timestamp
19/02/2002
19/02/2002
19/02/2002
19/02/2002
19/02/2002
19/02/2002
The dates are usually uniform, however, there are files with irregular dates pattern such as this example:
(abnormal_file.csv)
timestamp
19/02/2002
19/02/2003
19/02/2005
19/02/2006
In my directory, there are hundreds of files that consist of normal.csv and abnormal.csv.
I want to write a bash or awk script that detect the dates pattern in all files of a directory. Files with abnormal.csv should be moved automatically to a new, separate directory (let's say dir_different/).
Currently, I have tried the following:
#!/bin/bash
mkdir dir_different
for FILE in *.csv;
do
# pipe 1: detect the changes in the line
# pipe 2: print the timestamp column (first column, columns are comma-separated)
awk '$1 != prev {print ; prev = $1}' < $FILE | awk -F , '{print $1}'
done
If the timestamp in a given file is normal, then only one single timestamp will be printed; but for abnormal files, multiple dates will be printed.
I am not sure how to separate the abnormal files from the normal files, and I have tried the following:
do
output=$(awk 'FNR==3{print $0}' $FILE)
echo ${output}
if [[ ${output} =~ ([[:space:]]) ]]
then
mv $FILE dir_different/
fi
done
Or is there an easier method to detect changes in lines and separate files that have different lines? Thank you for any suggestions :)

Answer 1

Assuming that none of your "normal" CSV files have trailing newlines this should do the separation just fine:
#!/bin/bash
mkdir -p dir_different
for FILE in *.csv;
do
if awk '{a[$1]++}END{if(length(a)<=2){exit 1}}' "$FILE" ; then
echo mv "$FILE" dir_different
fi
done
After a dry-run just get rid of the echo :)
Edit:
{a[$1]++} This bit creates an array a that gets the first field of each line as an index, and that gets incremented every time the same value is seen.
END{if(length(a)<=2){exit 1}} This checks how many elements are in the array. If there there are less than 3 (which should be the case if there's always the same date and we only get 1 header, 1 date) exit the processing with 1.
"$FILE" is part of the bash script, not awk, and I quoted your variable out of habit, should you ever have files w/ spaces in their names you'll see why :)

Answer 2

So, a "normal" file contains only two different lines:
timestamp
dd/mm/yyyy
Testing if a file is normal is thus as simple as:
[ $(sort -u file.csv | wc -l) -eq 2 ]
This leads to the following possible solution:
#!/usr/bin/env bash
mkdir -p dir_different
for FILE in *.csv;
do
if [ $(sort -u "$FILE" | wc -l) -ne 2 ] ; then
echo mv "$FILE" dir_different
fi
done