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.TH SED 1

.SH NAME

sed \- stream editor

.SH SYNOPSIS

.B sed

[

.B -n

]

[

.B -g

]

[

.B -e

.I script

]

[

.B -f

.I sfile

]

[

.I file ...

]

.SH DESCRIPTION

.I Sed

copies the named

.I files

(standard input default) to the standard output,

edited according to a script of commands.

The

.B -f

option causes the script to be taken from file

.IR sfile ;

these options accumulate.

If there is just one

.B -e

option and no

.BR -f 's,

the option

.B -e

may be omitted.

The

.B -n

option suppresses the default output;

.B -g

causes all substitutions to be global, as if suffixed

.BR g .

.PP

A script consists of editing commands, one per line,

of the following form:

.IP

[\fIaddress\fR [\fL,\fI address\fR] ] \fIfunction\fR [\fIargument\fR ...] [\fL;\fP]

.PP

In normal operation

.I sed

cyclically copies a line of input into a

.I pattern space

(unless there is something left after

a

.L D

command),

applies in sequence

all commands whose

.I addresses

select that pattern space,

and at the end of the script copies the pattern space

to the standard output (except under

.BR -n )

and deletes the pattern space.

.PP

An

.I address

is either a decimal number that counts

input lines cumulatively across files, a

.L $

that

addresses the last line of input, or a context address,

.BI / regular-expression / \f1,

in the style of

.IR regexp (6),

with the added convention that

.L \en

matches a

newline embedded in the pattern space.

.PP

A command line with no addresses selects every pattern space.

.PP

A command line with

one address selects each pattern space that matches the address.

.PP

A command line with

two addresses selects the inclusive range from the first

pattern space that matches the first address through

the next pattern space that matches

the second.

(If the second address is a number less than or equal

to the line number first selected, only one

line is selected.)

Thereafter the process is repeated, looking again for the

first address.

.PP

Editing commands can be applied to non-selected pattern

spaces by use of the negation function

.L !

(below).

.PP

An argument denoted

.I text

consists of one or more lines,

all but the last of which end with

.L \e

to hide the

newline.

Backslashes in text are treated like backslashes

in the replacement string of an

.L s

command,

and may be used to protect initial blanks and tabs

against the stripping that is done on

every script line.

.PP

An argument denoted

.I rfile

or

.I wfile

must terminate the command

line and must be preceded by exactly one blank.

Each

.I wfile

is created before processing begins.

There can be at most 120 distinct

.I wfile

arguments.

.TP \w'\fL!\ \fIfunction\fL'u

.B a\e

.br

.ns

.TP

.I text

Append.

Place

.I text

on the output before

reading the next input line.

.TP

.BI b " label"

Branch to the

.B :

command bearing the

.IR label .

If

.I label

is empty, branch to the end of the script.

.TP

.B c\e

.br

.ns

.TP

.I text

Change.

Delete the pattern space.

With 0 or 1 address or at the end of a 2-address range, place

.I text

on the output.

Start the next cycle.

.TP

.B d

Delete the pattern space.

Start the next cycle.

.TP

.B D

Delete the initial segment of the

pattern space through the first newline.

Start the next cycle.

.TP

.B g

Replace the contents of the pattern space

by the contents of the hold space.

.TP

.B G

Append the contents of the hold space to the pattern space.

.TP

.B h

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

.TP

.B H

Append the contents of the pattern space to the hold space.

.ne 3

.TP

.B i\e

.br

.ns

.TP

.I text

Insert.

Place

.I text

on the standard output.

.TP

.B n

Copy the pattern space to the standard output.

Replace the pattern space with the next line of input.

.TP

.B N

Append the next line of input to the pattern space

with an embedded newline.

(The current line number changes.)

.TP

.B p

Print.

Copy the pattern space to the standard output.

.TP

.B P

Copy the initial segment of the pattern space through

the first newline to the standard output.

.TP

.B q

Quit.

Branch to the end of the script.

Do not start a new cycle.

.TP

.BI r " rfile"

Read the contents of

.IR rfile .

Place them on the output before reading

the next input line.

.TP

.B s/\fIregular-expression\fP/\fIreplacement\fP/\fIflags

Substitute the

.I replacement

string for instances of the

.I regular-expression

in the pattern space,

as per

.I regsub

in

.IR regexp (2).

Any character may be used instead of

.LR / .

For a fuller description see

.IR regexp (6).

.I Flags

is zero or more of

.RS

.TP

.B g

Global.

Substitute for all non-overlapping instances of the

.I regular expression

rather than just the

first one.

.TP

.B p

Print the pattern space if a replacement was made.

.TF "w\fI wfile "

.PD

.TP

.BI w " wfile"

Write.

Append the pattern space to

.I wfile

if a replacement

was made.

.RE

.TP

.BI t " label"

Test.

Branch to the

.L :

command bearing the

.I label

if any

substitutions have been made since the most recent

reading of an input line or execution of a

.LR t .

If

.I label

is empty, branch to the end of the script.

.TP

.BI w " wfile"

Write.

Append the pattern space to

.IR wfile .

.TP

.B x

Exchange the contents of the pattern and hold spaces.

.TP

.B y/\fIstring1\fP/\fIstring2\fP/

Transform.

Replace all occurrences of characters in

.I string1

with the corresponding character in

.IR string2 .

The lengths of

.I

string1

and

.I string2

must be equal.

.TP

.BI ! "function"

Don't.

Apply the

.I function

(or group, if

.I function

is

.LR { )

only to lines

.I not

selected by the address(es).

.TP

.B #

Comment.

Ignore the rest of the line.

.TP

.BI : " label"

This command does nothing; it bears a

.I label

for

.B b

and

.B t

commands to branch to.

.TP

.B =

Place the current line number on the standard output as a line.

.TP

.B {

Execute the following commands through a matching

.L }

only when the pattern space is selected.

.TP

.B " "

An empty command is ignored.

.ne 4

.SH EXAMPLES

.TP

.B sed 10q file

Print the first 10 lines of the file.

.TP

.B sed '/^$/d'

Delete empty lines from standard input.

.TP

.B sed 's/UNIX/& system/g'

Replace every instance of

.L UNIX

by

.LR "UNIX system" .

.PP

.EX

sed 's/ *$//	\fRdrop trailing blanks\fP

/^$/d		\fRdrop empty lines\fP

s/  */\e		\fRreplace blanks by newlines\fP

/g

/^$/d' chapter*

.EE

.ns

.IP

Print the files

.BR chapter1 ,

.BR chapter2 ,

etc. one word to a line.

.PP

.EX

nroff -ms manuscript | sed '

${

	/^$/p	\fRif last line of file is empty, print it\fP

}

//N			\fRif current line is empty, append next line\fP

/^\en$/D'		\fRif two lines are empty, delete the first\fP

.EE

.ns

.IP

Delete all but one of each group of empty lines from a

formatted manuscript.

.SH SOURCE

.B /sys/src/cmd/sed.c

.SH SEE ALSO

.IR ed (1),

.IR grep (1),

.IR awk (1),

.IR lex (1),

.IR sam (1),

.IR regexp (6)

.br

L. E. McMahon,

`SED \(em A Non-interactive Text Editor',

Unix Research System Programmer's Manual, Volume 2.

.SH BUGS

If input is from a pipe, buffering may consume

characters beyond a line on which a

.L q

command is executed.