Using Linux Commands

Lab 4

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Create empty files

To create an empty file

$ touch apple banana grape grapefruit watermelon

$ ls -l

Using file-matching metacharacters Metacharacters help to match one or more files without typing

each filename completely. * This matches any number of characters. ? This matches any one character. […] This matches any one of the characters between the

brackets, which can include a dash-separated rang of letters or numbers.

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$ ls a*

apple

$ ls g*

grape grapefruit

$ ls g*t

grapefruit

$ ls *e*

apple grape grapefruit watermelon

$ ls *n*

banana watermelon

Using file-matching metacharactersUsing file-matching metacharacters

This matches any number of characters *

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Using file-matching metacharactersUsing file-matching metacharacters

This matches any one character ?

$ ls ????e

Apple grape

$ ls g???e*

grape grapefruit

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Using file-matching metacharactersUsing file-matching metacharacters

This matches any one of the characters between the brackets […]

$ ls [abw]*

apple banana watermelon

$ ls [agw] * [ne]

grape grapefruit

$ ls [a-g] *

apple banana grape grapefruit

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Using file-redirection metacharactersUsing file-redirection metacharacters

$ mail root < ~/.bashrc

$ echo “I finished the project on $(date)” > ~/projects

• Direct the contents of a file to the command <

• Direct the output of a command to a file, overwritingoverwriting any existing file >

• Direct the output of a command to a file, addingadding the output to the end of existing file >>

$ echo “I finished the project on $(date)” >> ~/projects

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date commandsdate commands

Change or set current date and time.Syntax date [date or time string ]Examples Show current date & time

Set date to 2011-Mar-15

Set date as well as time

$ date

$date --date=“2011-3-15

$date --date=“2001-3-15 11:59 AM” 7

echo Commandecho Command

Use echo command to display text or value of variable.

echo [options] [string, variables...] Displays text or variables value on screen.

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echo Commandecho Command

Options-n Do not output the trailing new line.-e Enable interpretation of the following backslash escaped characters in the strings:

\a alert (bell)\b backspace\n new line\t horizontal tab

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QuotesQuotes

"Double Quotes" - Anything enclose in double quotes removed meaning of that characters (except \ and $).

'Single quotes' - Enclosed in single quotes remains unchanged.

`Back quote` -To execute command

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Examples of quoting special Examples of quoting special characterscharacters

$ echo ' My working directory is `pwd`'

My working directory is`pwd`

$ echo "My working directory is `pwd`”

My working directory is /home/jane

$ echo -e "An apple a day keeps away \a\t\tdoctor\n"

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Sort commandSort commandPiping commandPiping command

sort {file-name}sort {file-name} Options -r   Reverse normal order  (so "Z" starts the list instead of "A").

-n  Sort in numeric order-nr Sort in reverse numeric order

$ ls /etc/password | sort | less

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Sequential commandsSequential commands

To run a sequence of commands type several commands on the same command line and separating them with semicolons(;)

$ mkdir ng ; cd ng ; touch tom

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