413 lines
7.1 KiB
Text
413 lines
7.1 KiB
Text
.TH SED 1
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.SH NAME
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sed \- stream editor
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.SH SYNOPSIS
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.B sed
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[
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.B -n
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]
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[
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.B -g
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]
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[
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.B -e
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.I script
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]
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[
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.B -f
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.I sfile
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]
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[
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.I file ...
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]
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.SH DESCRIPTION
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.I Sed
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copies the named
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.I files
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(standard input default) to the standard output,
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edited according to a script of commands.
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The
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.B -f
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option causes the script to be taken from file
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.IR sfile ;
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these options accumulate.
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If there is just one
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.B -e
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option and no
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.BR -f 's,
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the option
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.B -e
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may be omitted.
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The
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.B -n
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option suppresses the default output;
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.B -g
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causes all substitutions to be global, as if suffixed
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.BR g .
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.PP
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A script consists of editing commands, one per line,
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of the following form:
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.IP
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[\fIaddress\fR [\fL,\fI address\fR] ] \fIfunction\fR [\fIargument\fR ...] [\fL;\fP]
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.PP
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In normal operation
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.I sed
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cyclically copies a line of input into a
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.I pattern space
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(unless there is something left after
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a
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.L D
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command),
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applies in sequence
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all commands whose
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.I addresses
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select that pattern space,
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and at the end of the script copies the pattern space
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to the standard output (except under
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.BR -n )
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and deletes the pattern space.
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.PP
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An
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.I address
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is either a decimal number that counts
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input lines cumulatively across files, a
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.L $
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that
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addresses the last line of input, or a context address,
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.BI / regular-expression / \f1,
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in the style of
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.IR regexp (6),
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with the added convention that
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.L \en
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matches a
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newline embedded in the pattern space.
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.PP
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A command line with no addresses selects every pattern space.
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.PP
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A command line with
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one address selects each pattern space that matches the address.
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.PP
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A command line with
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two addresses selects the inclusive range from the first
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pattern space that matches the first address through
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the next pattern space that matches
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the second.
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(If the second address is a number less than or equal
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to the line number first selected, only one
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line is selected.)
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Thereafter the process is repeated, looking again for the
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first address.
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.PP
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Editing commands can be applied to non-selected pattern
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spaces by use of the negation function
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.L !
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(below).
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.PP
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An argument denoted
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.I text
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consists of one or more lines,
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all but the last of which end with
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.L \e
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to hide the
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newline.
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Backslashes in text are treated like backslashes
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in the replacement string of an
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.L s
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command,
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and may be used to protect initial blanks and tabs
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against the stripping that is done on
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every script line.
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.PP
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An argument denoted
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.I rfile
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or
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.I wfile
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must terminate the command
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line and must be preceded by exactly one blank.
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Each
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.I wfile
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is created before processing begins.
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There can be at most 120 distinct
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.I wfile
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arguments.
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.TP \w'\fL!\ \fIfunction\fLXXX'u
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.B a\e
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.br
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.ns
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.TP
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.I text
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Append.
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Place
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.I text
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on the output before
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reading the next input line.
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.TP
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.BI b " label"
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Branch to the
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.B :
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command bearing the
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.IR label .
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If
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.I label
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is empty, branch to the end of the script.
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.TP
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.B c\e
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.br
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.ns
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.TP
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.I text
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Change.
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Delete the pattern space.
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With 0 or 1 address or at the end of a 2-address range, place
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.I text
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on the output.
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Start the next cycle.
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.TP
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.B d
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Delete the pattern space.
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Start the next cycle.
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.TP
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.B D
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Delete the initial segment of the
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pattern space through the first newline.
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Start the next cycle.
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.TP
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.B g
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Replace the contents of the pattern space
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by the contents of the hold space.
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.TP
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.B G
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Append the contents of the hold space to the pattern space.
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.TP
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.B h
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Replace the contents of the hold space by the contents of the pattern space.
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.TP
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.B H
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Append the contents of the pattern space to the hold space.
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.ne 3
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.TP
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.B i\e
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.br
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.ns
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.TP
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.I text
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Insert.
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Place
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.I text
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on the standard output.
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.TP
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.B n
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Copy the pattern space to the standard output.
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Replace the pattern space with the next line of input.
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.TP
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.B N
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Append the next line of input to the pattern space
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with an embedded newline.
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(The current line number changes.)
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.TP
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.B p
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Print.
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Copy the pattern space to the standard output.
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.TP
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.B P
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Copy the initial segment of the pattern space through
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the first newline to the standard output.
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.TP
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.B q
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Quit.
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Branch to the end of the script.
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Do not start a new cycle.
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.TP
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.BI r " rfile"
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Read the contents of
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.IR rfile .
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Place them on the output before reading
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the next input line.
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.TP
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.B s/\fIregular-expression\fP/\fIreplacement\fP/\fIflags
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Substitute the
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.I replacement
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string for instances of the
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.I regular-expression
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in the pattern space.
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Any character may be used instead of
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.LR / .
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For a fuller description see
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.IR regexp (6).
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.I Flags
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is zero or more of
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.RS
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.TP
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.B g
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Global.
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Substitute for all non-overlapping instances of the
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.I regular expression
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rather than just the
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first one.
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.TP
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.B p
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Print the pattern space if a replacement was made.
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.TP
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.BI w " wfile"
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Write.
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Append the pattern space to
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.I wfile
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if a replacement
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was made.
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.RE
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.IP
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An ampersand
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.L &
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appearing in the replacement
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is replaced by the string matching the regular expression.
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The characters
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.BI \e n\f1,
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where
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.I n
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is a digit,
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are replaced by the text matched by the
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.IR n -th
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regular subexpression
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enclosed between
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.L (
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and
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.LR ) .
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When
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nested parenthesized subexpressions
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are present,
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.I n
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is determined by counting occurrences of
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.L (
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starting from the left.
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.TP
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.BI t " label"
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Test.
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Branch to the
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.L :
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command bearing the
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.I label
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if any
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substitutions have been made since the most recent
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reading of an input line or execution of a
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.LR t .
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If
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.I label
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is empty, branch to the end of the script.
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.TP
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.B w
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.I wfile
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.br
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Write.
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Append the pattern space to
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.IR wfile .
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.TP
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.B x
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Exchange the contents of the pattern and hold spaces.
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.TP
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.B y/\fIstring1\fP/\fIstring2\fP/
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Transform.
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Replace all occurrences of characters in
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.I string1
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with the corresponding character in
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.IR string2 .
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The lengths of
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.I
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string1
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and
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.I string2
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must be equal.
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.TP
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.BI ! "function"
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Don't.
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Apply the
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.I function
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(or group, if
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.I function
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is
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.LR { )
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only to lines
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.I not
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selected by the address(es).
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.TP
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.B #
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Comment.
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Ignore the rest of the line.
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.TP
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.BI : " label"
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This command does nothing; it bears a
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.I label
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for
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.B b
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and
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.B t
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commands to branch to.
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.TP
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.B =
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Place the current line number on the standard output as a line.
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.TP
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.B {
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Execute the following commands through a matching
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.L }
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only when the pattern space is selected.
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.TP
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.B " "
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An empty command is ignored.
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.ne 4
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.SH EXAMPLES
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.TP
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.B sed 10q file
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Print the first 10 lines of the file.
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.TP
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.B sed '/^$/d'
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Delete empty lines from standard input.
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.TP
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.B sed 's/UNIX/& system/g'
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Replace every instance of
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.L UNIX
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by
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.LR "UNIX system" .
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.PP
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.EX
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sed 's/ *$// \fRdrop trailing blanks\fP
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/^$/d \fRdrop empty lines\fP
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s/ */\e \fRreplace blanks by newlines\fP
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/g
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/^$/d' chapter*
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.EE
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.ns
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.IP
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Print the files
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.BR chapter1 ,
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.BR chapter2 ,
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etc. one word to a line.
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.PP
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.EX
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nroff -ms manuscript | sed '
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${
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/^$/p \fRif last line of file is empty, print it\fP
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}
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//N \fRif current line is empty, append next line\fP
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/^\en$/D' \fRif two lines are empty, delete the first\fP
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.EE
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.ns
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.IP
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Delete all but one of each group of empty lines from a
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formatted manuscript.
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.SH SOURCE
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.B /sys/src/cmd/sed.c
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.SH SEE ALSO
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.IR ed (1),
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.IR grep (1),
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.IR awk (1),
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.IR lex (1),
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.IR sam (1),
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.IR regexp (6)
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.br
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L. E. McMahon,
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`SED \(em A Non-interactive Text Editor',
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Unix Research System Programmer's Manual, Volume 2.
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.SH BUGS
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If input is from a pipe, buffering may consume
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characters beyond a line on which a
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.L q
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command is executed.
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