Loop over files in HDFS directory

Question

I need to loop over all csv files in a Hadoop file system. I can list all of the files in a HDFS directory with

> hadoop fs -ls /path/to/directory
Found 2 items
drwxr-xr-x   - hadoop hadoop          2 2016-10-12 16:20 /path/to/directory/tmp
-rwxr-xr-x   3 hadoop hadoop 4691945927 2016-10-12 19:37 /path/to/directory/myfile.csv

and can loop over all files in a standard directory with

for filename in /path/to/another/directory/*.csv; do echo $filename; done

but how can I combine the two? I've tried

for filename in `hadoop fs -ls /path/to/directory | grep csv`; do echo $filename; done

but that gives me some nonsense like

Found
2
items
drwxr-xr-x

hadoop
hadoop
2    
2016-10-12
....

Aitken

hadoop fs -ls /path/to/directory | grep csv should give you a list of lines of standard out, not necessarily just filenames. – Nichols

See in another question a nice way todo a loop: #28685971 – Rellia

Answer 1

This should work

for filename in `hadoop fs -ls /path/to/directory | awk '{print $NF}' | grep .csv$ | tr '\n' ' '`
do echo $filename; done

Radiophotograph

This works like a charm! But it prints the entire path to the file. How can I cut it short so that it prints only the file name?? – Coreligionist

For anyone looking for a similar solution, use 'cut' to get the substring. $(echo $filename | cut -f4 -d/) – Coreligionist

I can refer to #965553 for short – Radiophotograph

It would be great if someone could explain how this works – Fisticuffs

It works for me when I run it in the shell, but when I run it through a script, the loop runs only once. The output is a single string that contains the full filename of each file in the directory. The trim operation removes the newline character and replaces it with a space and turns every line of the -ls output to a single space separated line. How can I fix this? – Shiite

Answer 2

The -C option will display only the file paths.

for filename in $(hadoop fs -ls -C /path/to/directory/*.csv); do
    echo "${filename}"
done

Ambagious