Grep duplicate JSON keys

If you have large JSON files with application settings in, you need to be sure that the settings only appear once. Not a problem until you get to the stage of very large files, being edited by all sorts of people manually.

"setting_1" : "some value",
"setting_2" : "another value",
"setting_1" : "different again"

Run a script to check for duplicate key names:

grep -Po '"[a-z_0-9]+"[ ]*:' <filename> | uniq -d

The above will output the duplicated setting(s) if any, to the console. Tested on Ubuntu 12.04

Find a file containing a text string on Linux

There is a very useful command in Linux, called grep. It is a utility for searching plain text files using regular expressions. You can either search files and folders as a parameter, or pipe command outputs to it, such as grep’ing a tail.

For looking for a file:

grep -r "string to find" /folder/to/look/in/

Thats the simple answer.

If you want to pipe the grep to monitor say a tail

tail -f /var/log/maillog | grep ""