🧠 Recap on filters

wc

• Summarises its input as a single line
• Often useful as the last command in pipeline
• -c to print the number of characters
• -w to print the number of words
• -l to print the number of lines
• By default, wc prints the number of lines, words and characters in its input

tr

• Reads characters and writes characters
• Maps some characters with others
• Format: tr sourceChars destChars
• tr doesn’t accept file names on the command line → uses stdin only
• Not line-based, works with individual chars
• Shorthands are available for specifying a range of chars
• -c maps all bytes not occurring in the source characters
• -s squeeze adjacent repeated characters
• -d delete all characters in the source characters

head/tail