tr

tr linux command cheatsheet by Thamizhiniyan C S

Introduction

Translate command(tr) can help you in number of ways, ranging from changing character cases in a string to replacing characters in a string.

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Syntax

tr [flags] [source]/[find]/[select] [destination]/[replace]/[change]

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Important Flags

Flags	Description
-d	To delete a given set of characters
-t	To concat source set with destination set(destination set comes first; t stands for truncate)
-s	To replace the source set with the destination set(s stands for squeeze)
-c	This is the REVERSE card in this game, for eg. If you specify -c with -d to delete a set of characters then it will delete the rest of the characters leaving the source set which we specified (c stands for complement; as in doing reverse of something)
[:alnum:]	all letters and digits
[:alpha:]	all letters
[:blank:]	all horizontal whitespace
[:cntrl:]	all control characters
[:digit:]	all digits
[:graph:]	all printable characters, not including space
[:lower:]	all lower case letters
[:print:]	all printable characters, including space
[:punct:]	all punctuation characters
[:space:]	all horizontal or vertical whitespace
[:upper:]	all upper case letters
[:xdigit:]	all hexadecimal digits
[=CHAR=]	all characters which are equivalent to CHAR

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Examples

Commands	Description
cat file.txt | tr -s '[a-z]' '[A-Z]'	Convert every alphabetic character to upper case
cat file.txt | tr -s '[:lower:]' '[:upper:]'	Convert every alphabetic character to upper case
cat creds.txt | tr -d '[a-zA-Z: ]'	To view creds of a user which are in digits
tr '()' '[]'	To replace all parentheses ( ) with box brackets [ ]
tr -d a-z	To delete all the lowercase characters a-z
tr -s ' '	To replace all sequences of multiple spaces with just one space
tr [:space:] "\t"	Translates all the white-space characters to tabs
tr -d [:digit:]	To remove all the digits from the string
tr -cd [:digit:]	To remove all characters except digits ( complement )
tr -cs 'i' '0'	Replaces all characters except i with 0 and then squeezes the repeated 0 characters
tr -cs '[:alnum:]' '\n'	To put each word in a new line
tr -s '\n'	To delete the blank lines simply squeeze the repetitive newline characters
echo $PATH | tr ':' '\n'	To print each directory on a separate line from the PATH environment variable