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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

Buy it now, or read it online on Safari Bookshelf.



tr

tr [options] [string1 [string2] ]

Translate characters. Copy standard input to standard output, substituting characters from string1 to string2, or deleting characters in string1.

Options

-c, --complement

Complement characters in string1 with respect to ASCII 001-377.

-d, --delete

Delete characters in string1 from output.

-s, --squeeze-repeats

Squeeze out repeated output characters in string2.

-t, --truncate-set1

Truncate string1 to the length of string2 before translating.

--help

Print help message and then exit.

--version

Print the version number and then exit.

Special characters

Include brackets ([ ] ) where shown.

\a

Ctrl-G (bell)

\b

Ctrl-H (backspace)

\f

Ctrl-L (form feed)

\n

Ctrl-J (newline)

\r

Ctrl-M (carriage return)

\t

Ctrl-I (tab)

\v

Ctrl-K (vertical tab)

\nnn

Character with octal value nnn

\\

Literal backslash

char1-char2

All characters in the range char1 through char2. If char1 does not sort before char2, produce an error.

[char*]

In string2, expand char to the length of string1.

[char*number]

Expand char to number occurrences. [x*4] expands to xxxx, for instance.

[:class:]

Expand to all characters in class, where class can be:

alnum

Letters and digits

alpha

Letters

blank

Whitespace

cntrl

Control characters

digit

Digits

graph

Printable characters except space

lower

Lowercase letters

print

Printable characters

punct

Punctuation

space

Whitespace (horizontal or vertical)

upper

Uppercase letters

xdigit

Hexadecimal digits

[=char=]

The class of characters to which char belongs.

Examples

Change uppercase to lowercase in a file:

cat file | tr 'A-Z' 'a-z'

Turn spaces into newlines (ASCII code 012):

tr ' ' ' ' < file

Strip blank lines from file and save in new.file (or use 011 to change successive tabs into one tab):

cat file | tr -s "" " " > new.file

Delete colons from file and save result in new.file:

tr -d : < file > new.file


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