Process text stream with filters

cat - Concatenate and display file contents

Example: cat file.txt | tr 'a-z' 'A-Z'

• This command displays the contents of file.txt and converts all lowercase letters to uppercase1.

cut - Remove sections from lines

Example: cat /etc/passwd | cut -d: -f1,7

• This extracts the username and shell fields from the passwd file5.

head - Display the beginning of a file

Example: cat long_file.txt | head -n 5

• This shows the first 5 lines of long_file.txt1.

tail - Display the end of a file

Example: cat log_file.txt | tail -n 10

• This displays the last 10 lines of log_file.txt1.

sort - Sort lines of text

Example: cat unsorted.txt | sort -n

• This sorts the contents of unsorted.txt numerically15.

uniq - Remove duplicate lines

Example: cat duplicates.txt | sort | uniq

• This removes duplicate lines from duplicates.txt after sorting15.

tr - Translate or delete characters

Example: echo "Hello, World!" | tr '[:lower:]' '[:upper:]' This converts all lowercase letters to uppercase3.

sed - Stream editor for filtering and transforming text

Example: cat file.txt | sed 's/old/new/g'

• This replaces all occurrences of "old" with "new" in file.txt5.

wc - Print newline, word, and byte counts

Example: cat document.txt | wc -w

• This counts the number of words in document.txt1.

These commands can be combined using pipes (|) to create powerful text processing workflows. For example:

• cat log.txt | grep "ERROR" | cut -d' ' -f8 | sort | uniq -c | sort -nr