Intermediate Unix Commands

This page contains just a teaser of some helpful commands. You should use man or search for more information about the commands, e.g., what arguments and flags you can use to customize the command.

UNIX organizes permissions by user, group, and others. There are three different permissions available: read, write, and execute

chmod is the command to change permissions

To change the group associated with a file, use chgrp

Gnu Regular Expression Print (grep) is a helpful tool to search for text within files, using–you guessed it–regular expressions! Regular expressions can be quite simple.

Example: I want to find all the names that start with “Sara” in a file of names

grep Sara names.txt

You can find files with various characteristics using the find command. It will look in the directory specified and all of its subdirectories. You can then apply a command to those found files.

Examples:

Find all of the files with the .txt extension in the current directory and its subdirectories

find . -name "*.txt"

Find all of the files in my home directory (and its subdirectories) that have no data in them (have 0 Bytes of data)

find ~ -size 0

View all of the information (e.g., last modified date) of all of the files in my home directory (and its subdirectories) that have no data in them

find ~ -size 0 -exec ls -l {} \;

Usage:

head <filename>

shows the first few lines of a file. You can use a flag to change how many lines are displayed

lsof -i :<port>

e.g.,

lsof -i :8080