sed.md

Use GNU sed only. brew install gnu-sed on macOS

Regular expressions

The default syntax is basic regular expression (BRE). The extended regular expression (ERE) is enabled with -E

The difference is in chars: ?,+,(),{},| (in BRE they match themselfs)

BRE - basic regular expressions

syntax	description
abc	matches "abc"
a*	0 or more a
.	any char including newline
^	beginning of line
$	end of line
[abc]	matches "a", "b" or "c"
[x-z]	matches "x", "y", "z"
[[:blank:]]	matches [:blank:] character class
a\+	one or more "a" (GNU extension)
\?	zero or one "a" (GNU extension)
\{i\}	As *, but matches exactly i sequences (i is a decimal integer; for portability, keep it between 0 and 255 inclusive)
\{i,j\}	Matches between i and j, inclusive, sequences
\{i,\}	Matches more than or equal to i sequences.
\(regexp\)	Groups the inner regexp as a whole, this is used to: - Apply postfix operators, like \(abcd\)*: this will search for zero or more whole sequences of "abcd", while abcd* would search for ‘abc’ followed by zero or more occurrences of ‘d’. Note that support for \(abcd\)* is required by POSIX 1003.1-2001, but many non-GNU implementations do not support it and hence it is not universally portable. - Use back references (see below).
regexp1|regexp2	Matches either regexp1 or regexp2. Use parentheses to use complex alternative regular expressions. The matching process tries each alternative in turn, from left to right, and the first one that succeeds is used. (GNU extension)
regexp1regexp2	Matches the concatenation of regexp1 and regexp2. Concatenation binds more tightly than |, ^, and $, but less tightly than the other regular expression operators.
\digit	Matches the digit-th \(…\) parenthesized subexpression in the regular expression. This is called a back reference. Subexpressions are implicitly numbered by counting occurrences of \( left-to-right.
\n	Matches the newline character.
\char	Matches char, where char is one of $, *, ., [, \, or ^. Note that the only C-like backslash sequences that you can portably assume to be interpreted are \n and \\; in particular \t is not portable, and matches a "t" under most implementations of sed, rather than a tab character

ERE - extended regular expressions

sed -E

syntax	description
abc	matches "abc"
a*	0 or more a
.	any char including newline
^	beginning of line
$	end of line
[abc]	matches "a", "b" or "c"
[x-z]	matches "x", "y", "z"
[[:blank:]]	matches [:blank:] character class
a+	one or more "a" (GNU extension)
?	zero or one "a" (GNU extension)
{i}	As *, but matches exactly i sequences (i is a decimal integer; for portability, keep it between 0 and 255 inclusive)
{i,j}	Matches between i and j, inclusive, sequences
{i,}	Matches more than or equal to i sequences.
(regexp)	Groups the inner regexp as a whole, this is used to: - Apply postfix operators, like (abcd)*: this will search for zero or more whole sequences of "abcd", while abcd* would search for ‘abc’ followed by zero or more occurrences of ‘d’. Note that support for (abcd)* is required by POSIX 1003.1-2001, but many non-GNU implementations do not support it and hence it is not universally portable. - Use back references (see below).
regexp1|regexp2	Matches either regexp1 or regexp2. Use parentheses to use complex alternative regular expressions. The matching process tries each alternative in turn, from left to right, and the first one that succeeds is used. (GNU extension)
regexp1regexp2	Matches the concatenation of regexp1 and regexp2. Concatenation binds more tightly than `
\digit	Matches the digit-th (…) parenthesized subexpression in the regular expression. This is called a back reference. Subexpressions are implicitly numbered by counting occurrences of \( left-to-right.
\n	Matches the newline character.
\char	Matches char, where char is one of $, *, ., [, \, or ^. Note that the only C-like backslash sequences that you can portably assume to be interpreted are \n and \\; in particular \t is not portable, and matches a "t" under most implementations of sed, rather than a tab character

character classes

class	description
[:alnum:]	Alphanumeric characters: [:alpha:] and [:digit:]; in the C locale and ASCII character encoding, this is the same as [0-9A-Za-z]
[:alpha:]	Alphabetic characters: [:lower:] and [:upper:]; in the C locale and ASCII character encoding, this is the same as [A-Za-z]
[:blank:]	Blank characters: space and tab
[:cntrl:]	Control characters. In ASCII, these characters have octal codes 000 through 037, and 177 (DEL). In other character sets, these are the equivalent characters, if any.
[:digit:]	Digits: 0 1 2 3 4 5 6 7 8 9
[:graph:]	Graphical characters: [:alnum:] and [:punct:]
[:lower:]	Lower-case letters; in the C locale and ASCII character encoding, this is a b c d e f g h i j k l m n o p q r s t u v w x y z
[:print:]	Printable characters: [:alnum:], [:punct:], and space
[:punct:]	Punctuation characters; in the C locale and ASCII character encoding, this is ! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~
[:space:]	Space characters: in the C locale, this is tab, newline, vertical tab, form feed, carriage return, and space
[:upper:]	Upper-case letters: in the C locale and ASCII character encoding, this is A B C D E F G H I J K L M N O P Q R S T U V W X Y Z