How to run grep on a single column?

Question

I want to grep the output of my ls -l command:

-rw-r--r--   1 root root       1866 Feb 14 07:47 rahmu.file
-rw-r--r--   1 rahmu user     95653 Feb 14 07:47 foo.file
-rw-r--r--   1 rahmu user   1073822 Feb 14 21:01 bar.file

I want to run grep rahmu on column $3 only, so the output of my grep command should look like this:

-rw-r--r--   1 rahmu user     95653 Feb 14 07:47 foo.file
-rw-r--r--   1 rahmu user   1073822 Feb 14 21:01 bar.file

What's the simplest way to do it? The answer must be portable across many Unices, preferably focusing on Linux and Solaris.

NB: I'm not looking for a way to find all the files belonging to a given user. This example was only given to make my question clearer.

Answer 1

One more time awk saves the day!

Here's a straightforward way to do it, with a relatively simple syntax:

ls -l | awk '{if ($3 == "rahmu") print $0;}'

or even simpler: (Thanks to Peter.O in the comments)

ls -l | awk '$3 == "rahmu"' 

Answer 2

If you are looking to match only part of the string on a given column, you can use advice from https://stackoverflow.com/questions/17001849/awk-partly-string-match-if-column-partly-matches

some_command | awk '$6 ~ /string/'

Answer 3

If by column, you mean fixed-size column, you could:

ls -l | grep "^.\{15\}rahmu"

where ^ means the beginning of the line, . means any character and \{15\} means exactly 15 occurrences of the previous character (any character in this case).

Answer 4

I know I'm late to the party, but I believe a very general solution to this problem is to use awk with regular expressions like so:

awk '$3~/rahmu/{print}' input_file

The part enclosed by '//' can be any kind of regular expression.

Answer 5

To grep based on single username column (and print only files), you can try:

ls -la | grep "^-\S\+\s\+\S\+\s\+rahmu"

For directories, change - into d, for any type remove -.

It basically selects each column by \S\+\s\+ which matches a non-space characters followed by a space characters, so we're matching three first columns and then the username.