Addresses¶

A sed address is either a line number or a pattern, which may be combined arbitrarily to construct ranges. Lines are numbered across all input files.

Any address may be followed by an exclamation mark ('"!"'), selecting all lines not matching that address.

number

The line with the given number is selected.

$

A dollar sign ("$") is the line number of the last line of the input stream.

/regular expression/

A pattern address is a basic regular expression (see "BASIC REGULAR EXPRESSIONS"), between the delimiting character "/". Any other character except "\" or newline may be used to delimit a pattern address when the initial delimiter is prefixed with a backslash ('"\"').

If no address is given, the command selects every line.

If one address is given, it selects the line (or lines) matching the address.

Two addresses select a range that begins whenever the first address matches, and ends (including that line) when the second address matches. If the first (second) address is a matching pattern, the second address is not applied to the very same line to determine the end of the range. Likewise, if the second address is a matching pattern, the first address is not applied to the very same line to determine the begin of another range. If both addresses are line numbers, and the second line number is less than the first line number, then only the first line is selected.

Functions¶

The maximum permitted number of addresses is indicated with each function synopsis below.

The argument text consists of one or more lines following the command. Embedded newlines in text must be preceded with a backslash. Other backslashes in text are deleted and the following character is taken literally.

[1addr]a\ text

Write text (which must start on the line following the command) to standard output immediately before reading the next line of input, either by executing the N function or by beginning a new cycle.

[2addr]b [label]

Branch to the : function with the specified label. If no label is given, branch to the end of the script.

[2addr]c\ text

The line, or range of lines, selected by the address is deleted. The text (which must start on the line following the command) is written to standard output. With an address range, this occurs at the end of the range.

[2addr]d

Deletes the pattern space and starts the next cycle.

[2addr]D

Deletes the pattern space through the first embedded newline or to the end. If the pattern space becomes empty, a new cycle is started, otherwise execution of the script is restarted.

[2addr]g

Replace the contents of the pattern space with the hold space.

[2addr]G

Append a newline and the contents of the hold space to the pattern space.

[2addr]h

Replace the contents of the hold space with the pattern space.

[2addr]H

Append a newline and the contents of the pattern space to the hold space.

[1addr]i\ text

Write the text (which must start on the line following the command) to standard output.

[2addr]l

Print the contents of the pattern space: non-printable characters are shown in C-style escaped form; long lines are split and have a trailing ^'"\"' at the point of the split; the true end of a line is marked with a '"$"'. Escapes are: '\a', '\t', '\n', '\f', '\r', '\e' for BEL, HT, LF, FF, CR, ESC, respectively, and '\' followed by a three-digit octal number for all other non-printable characters.

[2addr]n

If automatic printing is enabled, write the pattern space to the standard output. Replace the pattern space with the next line of input. If there is no more input, processing is terminated.

[2addr]N

Append a newline and the next line of input to the pattern space. If there is no more input, processing is terminated.

[2addr]p

Print the pattern space to the standard output. (Use the -n option to suppress automatic printing at the end of a cycle if you want to avoid double printing of lines.)

[2addr]P

Prints the pattern space through the first embedded newline or to the end.

[1addr]q

Branch to the end of the script and quit without starting a new cycle.

[1addr]r file

Copy the contents of the file to standard output immediately before the next attempt to read a line of input. Any error encountered while reading file is silently ignored.

[2addr]s/regular expression/replacement/flags

Substitute the replacement string for the first substring in the pattern space that matches the regular expression. Any character other than backslash or newline can be used instead of a slash to delimit the regular expression and the replacement. To use the delimiter as a literal character within the regular expression and the replacement, precede the character by a backslash ('"\"').

Literal newlines may be embedded in the replacement string by preceding a newline with a backslash.

Within the replacement, an ampersand ('"&"') is replaced by the string matching the regular expression. The strings '"\1"' through '"\9"' are replaced by the corresponding subpattern (see "BASIC REGULAR EXPRESSIONS"). To get a literal '"&"' or '"\"' in the replacement text, precede it by a backslash.

The following flags modify the behaviour of the s command:

[2addr]t [label]

Branch to the : function with the specified label if any s substitutions have been made since the most recent reading of an input line or execution of a t function. If no label is given, branch to the end of the script.

[2addr]w file

The contents of the pattern space are written to the file.

[2addr]x

Swap the contents of the pattern space and the hold space.

[2addr]y/string1/string2/

In the pattern space, replace all characters occurring in string1 by the character at the corresponding position in string2. It is possible to use any character (other than a backslash or newline) instead of a slash to delimit the strings. Within string1 and string2, a backslash followed by any character other than a newline is that literal character, and a backslash followed by an 'n' is replaced by a newline character.

[1addr]=

Prints the current line number on the standard output.

[0addr]: [label]

The command specifies the position of the label. It has no other effect.

[2addr]{ [command]

[0addr]}

These two commands begin and end a command list. The first command may be given on the same line as the opening { command. The commands within the list are jointly selected by the address(es) given on the { command (but may still have individual addresses).

[0addr]# [comment]

The entire line is ignored (treated as a comment). If, however, the first two characters in the script are '"#n"', automatic printing of output is suppressed, as if the -n option were given on the command line.

Atoms¶

The possible atoms of a BRE are: ., matching any single character; ^ and $, matching the null string at the beginning or end of a string, respectively; a bracket expressions, enclosed in [ and ] (see below); and any single character with no other significance (matching that character). A \ before one of: ., ^, $, [, *, \, matching the character after the backslash. A sequence of atoms enclosed in \( and \) becomes an atom and establishes the target for a backreference, consisting of the substring that actually matches the enclosed atoms. Finally, \ followed by one of the digits 0 through 9 is a backreference.

A ^ that is not first, or a $ that is not last does not have a special significance and need not be preceded by a backslash to become literal. The same is true for a ], that does not terminate a bracket expression.

An unescaped backslash cannot be last in a BRE.

Bounds¶

The BRE bounds are: *, specifying 0 or more matches of the preceding atom; \{count\}, specifying that many repetitions; \{minimum,\}, giving a lower limit; and \{minimum,maximum\} finally defines a lower and upper bound.

A bound appearing as the first item in a BRE is taken literally.

Bracket Expressions¶

A bracket expression is a list of characters, character ranges and character classes enclosed in [ and ] and matches any single character from the represented set of characters.

A character range is written as two characters separated by - and represents all characters (according to the character collating sequence) that are not less than the first and not greater than the second. (Ranges are very collating-sequence-dependent, and portable programs should avoid relying on them.)

A character class is one of the class names

   alnum     digit     punct
   alpha     graph     space
   blank     lower     upper
   cntrl     print     xdigit

enclosed in [: and :] and represents the set of characters as defined in ctype(3).

If the first character after [ is ^, the sense of matching is inverted.

To include a literal '"^"', place it anywhere else but first. To include a literal '"]"' place it first or immediately after an initial ^. To include a literal '"-"' make it the first (or second after ^) or last character, or the second endpoint of a range.

The special bracket expression constructs "[[:<:]]" and "[[:>:]]" match the null string at the beginning and end of a word respectively. (Note that neither is identical to Perl's '\b' atom.)

Additional Atoms¶

Since some sed implementations provide additional regular expression atoms (not defined in POSIX 1003.2), psed is capable of translating the following backslash escapes:

\< This is the same as "[[:>:]]".

\> This is the same as "[[:<:]]".

\w This is an abbreviation for "[[:alnum:]_]".

\W This is an abbreviation for "[^[:alnum:]_]".

\y Match the empty string at a word boundary.

\B Match the empty string between any two either word or non-word characters.

To enable this feature, the environment variable PSEDEXTBRE must be set to a string containing the requested characters, e.g.: "PSEDEXTBRE='<>wW'".