Find regular expression matching condition - linux

Question

I have a set of files including a date in their name:
MERRA2_400.tavg1_2d_slv_Nx.20151229.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151230.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151231.SUB.nc
I want to select the files matching a condition on this date. In this example: date > 20151230
I tried things like:
find . -regex ".*.SUB.nc" | cut -d "." -f 4 | while read a; do if [ $a -ge 20151201 ]; then echo $a; fi; done
BUT:
1) This is returning only a part of the filename, whereas I would like to return the entire filename.
2) There may be a more elegant way than using while read/do
thanks in advance!

Answer 1

Rearranging your code becomes:
#!/usr/bin/env bash
find . -regex ".*.SUB.nc" \
| rev | cut -d '.' -f 3 | rev \
| while read a; do
if [ $a -ge 20151201 ]; then
echo $a
fi
done
rev | cut -d '.' -f 3 | rev is used because
if you give absolute path or
the subdirectories have . in them
then it won't be the 4th field, but it will always be the 3rd last field.
This will give the output:
20151231
20151229
20151230
To show the complete file names change echo $a with ls *$a*. Output:
MERRA2_400.tavg1_2d_slv_Nx.20151231.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151229.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151230.SUB.nc
I tested this script with file names whose dates are less than 20151201. For example MERRA2_400.tavg1_2d_slv_Nx.20151200.SUB.nc. The results are consistent.
Perhaps a more efficient way to accomplish your task is using a grep regex like:
find . -regex ".*.SUB.nc" | grep -E "201512(0[1-9]|[1-9][0-9])|201[6-9][0-9][0-9][0-9]"

Answer 2

This will work just fine.
find . -regex ".*.SUB.nc" | rev | cut -d '.' -f 3 | rev | while read a; do if [ $a -ge 20151201 ]; then echo `ls -R | grep $a` ;fi ;done
rev | cut -d '.' -f 3 | rev is used because
if you give absolute path or
the subdirectories have . in them
then it won't be the 4th field now, but it will always be the 3rd last field always.
ls -R | grep $a so that you can recursively find out the name of the file.
Assume is the files and file structure is :
[root#localhost temp]# ls -lrt -R
.:
total 8
-rw-r--r--. 1 root root 0 Apr 25 16:15 MERRA2_400.tavg1_2d_slv_Nx.20151231.SUB.nc
-rw-r--r--. 1 root root 0 Apr 25 16:15 MERRA2_400.tavg1_2d_slv_Nx.20151230.SUB.nc
-rw-r--r--. 1 root root 0 Apr 25 16:15 MERRA2_400.tavg1_2d_slv_Nx.20151229.SUB.nc
drwxr-xr-x. 2 root root 4096 Apr 25 16:32 temp.3
drwxr-xr-x. 3 root root 4096 Apr 25 17:13 temp2
./temp.3:
total 0
./temp2:
total 4
-rw-r--r--. 1 root root 0 Apr 25 16:27 MERRA2_400.tavg1_2d_slv_Nx.20151111.SUB.nc
-rw-r--r--. 1 root root 0 Apr 25 16:27 MERRA2_400.tavg1_2d_slv_Nx.20151222.SUB.nc
drwxr-xr-x. 2 root root 4096 Apr 25 17:13 temp21
./temp2/temp21:
total 0
-rw-r--r--. 1 root root 0 Apr 25 17:13 MERRA2_400.tavg1_2d_slv_Nx.20151333.SUB.nc
Running above command gives :
MERRA2_400.tavg1_2d_slv_Nx.20151229.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151231.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151230.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151333.SUB.nc
MERRA2_400.tavg1_2d_slv_Nx.20151222.SUB.nc