CIS120Linux Fundementals

tr, sed and aspell Commands

tr Command

The tr command in Linux is used for translating or deleting characters from the input provided. It reads from standard input and writes to standard output.

Common Options for tr:

Option	Description
-d	Delete characters from the input
-s	Squeeze repeated characters into a single character
-c	Complement the set of characters

Examples:

Consider a file example.txt with the following content:

hello world
hello universe

To convert all lowercase characters to uppercase, you can use:

cat example.txt | tr 'a-z' 'A-Z'

Output:

HELLO WORLD
HELLO UNIVERSE

To delete all vowels from the text:

cat example.txt | tr -d 'aeiou'

Output:

hll wrld
hll nvrse

To change the blank space between two words to a hyphen:

cat example.txt | tr ' ' '-'

Output:

hello-world
hello-universe

To change all blank spaces (including tabs) to a hyphen using [[:blank:]]:

cat example.txt | tr '[[:blank:]]' '-'

Output:

hello-world
hello-universe

[[:blank:]] is a character class that matches all horizontal whitespace characters, which include spaces and tabs. This is useful when you want to ensure that all types of horizontal whitespace are replaced.

sed Command

The sed command, short for stream editor, is used to perform basic text transformations on an input stream (a file or input from a pipeline).

Common Options for sed:

Option	Description
-e	Add the script to the commands to be executed
-f	Add the script file
-i	Edit files in place
-n	Suppress automatic printing of pattern space

Examples:

Consider a file example.txt with the following content:

hello world
hello hello universe
hello everyone hello

To replace the first occurrence of the word "hello" with "hi" on each line:

sed 's/hello/hi/' example.txt

Output:

hi world
hi hello universe
hi everyone hello

To replace all occurrences of the word "hello" with "hi" using the global /g option:

sed 's/hello/hi/g' example.txt

Output:

hi world
hi hi universe
hi everyone hi

To delete lines containing the word "everyone":

sed '/everyone/d' example.txt

Output:

hello world
hello hello universe

aspell Command

The aspell command is a spell-checking utility in Linux. It can be used interactively to check the spelling of a document.

Common Options for aspell:

Option	Description
-c	Check a file
-a	Run in 'pipe mode'
-l	List available dictionaries
-d	Use a specific dictionary

Examples:

Consider a file example.txt with the following content:

helo wrld
hello everyone

To check the spelling of the file:

aspell check example.txt

Interactive mode will prompt corrections:

@(#) International Ispell Version 3.1.20 (but really Aspell 0.60.8)
 & helo 5 0: hello, he lo, halo, help, helot
 & wrld 8 0: world, word, weld, wild, wold, wrld's, WRLD, WLRD

To list available dictionaries:

aspell dicts

Output might include:

en
en_GB
en_US
fr
de
...

These commands are essential for text processing and transformation tasks in Linux, providing powerful tools for manipulating and validating text in various ways.