Search

More Grep

We already played with grep a bit, let's do a little bit more. First, let's learn what grep stands for: Global Regular Expression Print.

$ cat animals | grep "dog" $ grep "dog" animals

Both of those do the same thing. We can also search an entire directory by using the "*" symbol, often known as a wildcard. This wildcard will open every file in a directory.

$ grep "dog" *

As a note, you can also cat * in case you ever want to print every file in a directory. Many other commands use the wildcard operator.

If you only want to know which files in a directory have the target word, use "-l".

$ grep -l "dog" *

If you want to know the file name and line number, use "-n".

$ grep -n "dog" *

If you only want to see the lines in the file which don't have the term you are greping for, use "-v".

$ grep -v "dog" animals

This defaults to showing line numbers and file names, so if you only want to see the filenames, use "-l".

$ grep -l "dog" animals

Play around with a few of the grep settings to see what else is possible, but don't worry about memorizing them, stick to cheatsheets. And as always, the manpages are your best friend!

find

Alright, last command for the search section! While grep cared about searching through files, find only cares about file information!

Here are some example uses of find. There are a ton of flags for this, so use man anytime you need to do look for something you don't know the flags for

$ find directoryName -name secret 
> find all files named secret in a folder named directoryName 
$ find directoryName -type f -name "*.txt" 
> find all .txt files. Note the "*" wildcard 
$ find directoryName -type f -perm 0777 -print 
> find all files with the permission 0777. Don't worry too much about permissions yet. 
$ find directoryName -type f -name ".*" 
> find all secret files! The "." in front of the filename hides it from a standard ls. 
$ find / -user dennis 
> find all files from the root directory owned by the user dennis 
> remember that / by itself searches from root 
(which is a whole lot of searching, so it takes a few minutes)
 while ./ only searches from current directory. 
Looks similar but very different results. 
$ find / -size 50M 
> find all files from root that are 50MB 
$ find / -mtime 5 
> find all files modified in the last 5 days. 
Kind of useful from a forensics standpoint, though timestamps are unreliable!

This ain't everything but should be enough to help.

Assignment

Questions:
1. Write a command that will find all .html files on a computer that are 12 bytes in size, owned by "jake". 
   * You can make an example file by putting the contents "is this html" into a file and saving it as a .html file. 
   * However, getting the owner to be named Jake would require you to create a new user on your system and that is a bit of work
   * I recommend you just write one that will find ones owned by you, and then for your answer, submit the "Jake" version.
2. Write a command that finds any "hidden" (starts with . ) file in your user home folder.

Resources:
0. Google