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Learn command line

Please follow and complete the free online Bash Scripting Tutorial or Codecademy's Learn the Command Line. These are helpful tutorials. You should be able to go through these in a couple of hours.

Note: Bash is not installed on a PC. Rather, PC users must install Cygwin. Once Cygwin has been installed, the command line interface witll emulate bash. You can find all information regarding Cygwin here.

Q1. Cheat Sheet of Commands

Here's a list of items with which you should be familiar:

  • show current working directory path
  • creating a directory
  • deleting a directory
  • creating a file using touch command
  • deleting a file
  • renaming a file
  • listing hidden files
  • copying a file from one directory to another

Make a cheat sheet for yourself: a list of at least ten commands and what they do. (Use the 8 items above and add a couple of your own.)

  • print working directory:$ pwd
  • create directory: $ mkdir [options] <file_path>/<directory_name>
  • delete directory: $ rmdir [options] <file_path>/<directory_name>
  • create file with touch command: $ touch [options] <file_name>
  • delete file: $ rm [-i] <file_path>/<file_name>
  • rename file: $ mv <original_path/original_name> <original_path/new_name>
  • list hidden files: $ ls -a <path>
  • copy file from one directory to another: $ cp [options] <source> <destination>
  • display manual/documentation page for a command: $ man <command> or $ man -k <search_term>
  • search in a file for expressions: $ egrep [options] <expression(s)_to_search_for> <file>

Q2. List Files in Unix

What do the following commands do:

  • ls list all files in current directory, standard constraints
  • ls -a list all files, including hidden files
  • ls -l list all files with long listing
  • ls -lh list all files with long listing, with unit suffixes for file sizes
  • ls -lah list all files, including hidden files, with long listings and unit suffixes for file size
  • ls -t list all files sorted by most recent time modified
  • ls -Glp list all files with long listing, and colorized directory names followed by a / character

Q3. More List Files in Unix

Explore these other ls options and pick 5 of your favorites:

  • ls -r displays all files in reverse order. Ex: to display files ordered by most recently accessed: $ ls -ur
  • ls -R displays all subdirectories as well
  • ls -GF flags filenames with colorized output
  • ls -S list files sorted by size
  • ls -1 list all files with one output per line

Q4. Xargs

What does xargs do? Give an example of how to use it.

xargs is a tool for enacting an operation, action, or utility with a list of inputs. Example:

ls *.txt | xargs -n1 ./make_dated_copy.sh

The script make_dated_copy.sh makes a copy of an input file with the current date as a prefix to the input file name. In the example above, I find all the text files in the current directory and pipe the file names to the next part of the command. xargs accepts that list and sends the files, one at a time, to be operated on once (-n1) by the make_dated_copy.sh script. xargs will run the script on the input until it has exhaused the list.