Please follow and complete the free online Command Line Crash Course tutorial. This is a great, quick tutorial. Each "chapter" focuses on a command. Type the commands you see in the Do This section, and read the You Learned This section. Move on to the next chapter. You should be able to go through these in a couple of hours.
###Q1. Cheat Sheet of Commands
Make a cheat sheet for yourself: a list of at least ten commands and what they do, focused on things that are new, interesting, or otherwise worth remembering.
- man : Reads the manual page
- chmod : 'Change mode'. Changes the access permissions to files and directories
- find : used for searching files in a directory hierarchy
- grep : searches one/multiple files for a line that matches a pattern
- pushd : changes current directory to the location specified and stores the new directory on the directory stack
- popd : removes the top path from the directory stack and then returns to the previous directory
- chdown: changes ownership of a file system object
- less: Reads files. Allows both forward and backward movement
- cat : reads one or more files and prints them to standard output
- head: reads the first few lines of any text given to it as an input and writes them to standard output
###Q2. List Files in Unix
What do the following commands do:
ls
ls -a
ls -l
ls -lh
ls -lah
ls -t
ls -Glp
- ls : list files in this directory
- ls -a : lists all files including the hidden files
- ls -l : shows file or directory, size, modified date and time, file or folder name and owner of file and it’s permission
- ls -lh :same as above but shows size in 'human readable'
- ls -lah : same as lh but lists the hidden files too
- ls -t : Displays newest file first based on timestamp
- ls -Glp : Displays the files in long format but prevents owner info from being shown. Also, directories are shown as /
###Q3. More List Files in Unix
Explore these other ls options and pick 5 of your favorites:
- ls -ltr : shows latest modification file or directory
- ls -R : Recursively lists sub directories
- ls -S : Shows file size in order. Largest being the
- ls -d : Displays only directories
- ls -f : interprets name argument as directory and so can be used to search through directories
###Q4. Xargs
What does xargs do? Give an example of how to use it.
xargs executes some command from standard input. This can be done on a list of files or directories. Ex: find . -name "*.txt" | xargs grep "unix" The above command finds all the .txt files in the current or below directories and then searches for the word 'unix' in each .txt file