h1. Sed syntax

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This syntax format is described in standard "Unix sed utility in IEEE Std 1003.1-2001, Portable Operating SystemInterface (POSIX ), Shells and Utilities".

h2. Special match symbols

|<pre>^</pre>|begin of string|
|<pre>$</pre>|end of string|
|<pre>.</pre>|any symbol|
|<pre>*</pre>|previous value is repeated 0 or more times|
|<pre>+</pre>|previous value is repeated 1 or more times|
|<pre>{N}</pre>|previous value is repeated exactly N times|
|<pre>{N,M}</pre>|previous value is repeated from N to M times|
|<pre>[[:digit:]]</pre>|any digit|

To use specials symbols you need to screen them with '\'.
For example, '\+'.

h2. Special replacement symbols

|<pre>&</pre>|whole matched string|
|<pre>\1</pre>|1 matched atom|

h2. Examples

|*search*|*replace*|*result*|
|<pre>^011.*</pre>|<pre>777</pre>|string 011XXXXX will be replaced with string 777|
|<pre>^011</pre>|<pre>7</pre>|string 011XXXXXXX will be replaced with 7XXXXXXX|
|<pre>.*</pre>|<pre>00&</pre>|to all strings will be added a prefix 00. 
& - means "put original string"|
|<pre>^011</pre>||a prefix 011 will be cut|
|<pre>^(8)(.{10})$</pre>|<pre>7\2</pre>|strings 8ХХХХХХХХХХ will be replaced with 7ХХХХХХХХХ. 
All strings, which contain less or more 11 digits won't match this rule. 
Original string is split into 2 "atoms" - digit 8 and 10 remaining digits. 
\2 - means, that we put 2nd "atom" - 10 digits after 1st digit 8|
|<pre>(^.*)(.{2}$)</pre>|<pre>749511111\2</pre>|system remembers 2 last digits of original string and they are added to string in field "replace". 
Therefore, if original string was 444455, the resulting string will be 74951111155|
|<pre>.*</pre>|<pre>&</pre>|any value will pass without changes. 
& - means "put original string"|
|<pre>^[[:digit:]]*$</pre>|<pre>&</pre>|digital string will pass without changes. 
& - means "put original string"|
|<pre>^\+</pre>||prefix '+' will be cut.
'\' - is a symbol of screening of a special symbol '+'|

[[Синтаксис sed|Русский перевод]]